Migrate prod deploy from Swarm to K3s; add full deployment book

Infrastructure:
- Stack now runs on K3s v1.34.6 HA (3 Hetzner CX33 nodes as managers)
- Traefik DaemonSet + hostNetwork replaces Caddy + ingress mesh
- All manifests in deploy-k3s/manifests/; Swarm config (deploy/) kept
  temporarily for reference

Bug fixes surfaced during migration:
- Dockerfile: golang:1.24-alpine -> 1.25-alpine (go.mod requires 1.25)
- cache_service.go: remove sync.Once reassignment from inside Do()
  callback (was causing 'unlock of unlocked mutex' fatal after
  Redis Ping failure)
- router.go: relax CSP from 'default-src none' to 'default-src self'
  + allowlist fonts.googleapis.com so the marketing landing page CSS
  actually loads in browsers
- deploy/scripts/deploy_prod.sh: use docker buildx with
  --platform linux/amd64 so arm64 (Apple Silicon) dev machines produce
  images runnable on x86_64 Hetzner nodes; fix array expansion under
  set -u
- deploy/swarm-stack.prod.yml: fix secret source references to use
  top-level aliases (the '\${X_SECRET}' form never actually resolved);
  dozzle ports: long-form host_ip is rejected by Swarm, switched to
  short-form (bound to 0.0.0.0 with UFW-based loopback restriction);
  worker replicas 2 -> 1 (Asynq scheduler singleton)
- deploy-k3s/manifests/admin/deployment.yaml: probe path '/admin/' -> '/'
  (Next.js serves at root; /admin/ returned 404 and killed pods);
  startupProbe failureThreshold 12 -> 24
- deploy-k3s/manifests/pod-disruption-budgets.yaml: worker minAvailable
  1 -> 0 (singleton)
- deploy-k3s/manifests/api/deployment.yaml: startupProbe failureThreshold
  12 -> 48 (MigrateWithLock serializes across 3 replicas on first-boot;
  real startup takes up to 240s)
- .gitignore: tighten 'api' -> '/api' (was matching deploy-k3s/manifests/api/
  and admin/src/app/api/*, hiding legitimate files)

New files:
- deploy-k3s/manifests/traefik-helmchartconfig.yaml: DaemonSet +
  hostNetwork override for k3s-bundled Traefik
- deploy-k3s/manifests/ingress/ingress-simple.yaml: plain Ingress
  without TLS (CF Flexible SSL) and without middleware
- deploy-k3s/MIGRATION_NOTES.md: operator-facing migration log

Documentation:
- docs/deployment/ — full deployment book, 26 files, ~42k words:
  - Part I Overview, infrastructure, orchestrator choice (Ch 0-2)
  - Part II Networking, firewall, Cloudflare (Ch 3-4, 13)
  - Part III Security, Traefik ingress (Ch 5-6)
  - Part IV Services, DB, storage, secrets, registry (Ch 7-11)
  - Part V Data flow, deploy process, observability, failures, runbook
    (Ch 12, 14-17)
  - Part VI Cost, Swarm postmortem, roadmap (Ch 18-20)
  - Appendices: glossary, kubectl cheat sheet, file locations,
    consolidated citations
- README.md: Production Deployment section replaced with pointer to
  the book; Go version bumped to 1.25

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs/deployment/20-roadmap.md

@@ -0,0 +1,318 @@
+# 20 — Roadmap
+
+## Summary
+
+A consolidated list of known gaps, improvements, and scaling triggers.
+Items are grouped by category and roughly ordered by priority. This is
+the "if we had more time" list referenced throughout the book.
+
+## High priority (do soon)
+
+### Uptime monitoring
+
+**Why**: Right now we find out the site is down when users complain.
+
+**How**: Set up Uptime Kuma (self-hosted) or Better Stack Uptime
+(free tier) to ping `https://api.myhoneydue.com/api/health/` every
+minute, with Slack/email alerts on failure.
+
+**Effort**: ~30 min for Uptime Kuma deploy, ~10 min for Better Stack
+signup.
+
+### Cloudflare origin IP restriction
+
+**Why**: UFW allows :80 from anywhere. If node IPs leak, direct-connect
+attackers bypass CF's WAF/DDoS protection.
+
+**How**: Replace the anywhere-80 UFW rule with 15 IPv4 + 7 IPv6 CF
+ranges. See [Chapter 13 §CF IP ranges](./13-cloudflare.md#cloudflare-ip-ranges-used-in-traefik-trustedips).
+
+Automation: a small script that refreshes the CF IP list monthly and
+re-applies UFW rules.
+
+**Effort**: 1 hour.
+
+### Enable network policies in k3s
+
+**Why**: Currently pods can freely egress anywhere. A compromised pod
+could exfiltrate data or attack lateral services.
+
+**How**: `kubectl apply -f deploy-k3s/manifests/network-policies.yaml`.
+The scaffold defines default-deny + explicit allows for:
+- DNS egress for all pods
+- Traefik → api (port 8000)
+- Traefik → admin (port 3000)
+- api/worker → Redis
+- api/worker → external services (Postgres, B2, Fastmail)
+
+Then test that nothing breaks (might need to adjust allow rules).
+
+**Effort**: 1-2 hours including testing.
+
+### Apply Traefik security middleware
+
+**Why**: Our current Ingress has no rate limiting or security headers
+beyond what Traefik adds by default.
+
+**How**: Apply `deploy-k3s/manifests/ingress/middleware.yaml`, annotate
+Ingresses to use them:
+
+```yaml
+metadata:
+  annotations:
+    traefik.ingress.kubernetes.io/router.middlewares: honeydue-security-headers@kubernetescrd,honeydue-rate-limit@kubernetescrd
+```
+
+**Effort**: 15 min.
+
+## Medium priority
+
+### Upgrade to CF Full (strict) SSL
+
+**Why**: Currently CF↔origin is plain HTTP. An attacker between CF and
+Hetzner could read traffic. Full (strict) mode encrypts this leg with
+a CF-issued origin cert.
+
+**How**:
+1. Generate Origin CA cert in CF dashboard → SSL/TLS → Origin Server
+2. Create `cloudflare-origin-cert` Secret in k8s
+3. Add `tls:` block to Ingresses
+4. Switch CF SSL mode to Full (strict)
+
+**Effort**: 30 min.
+
+**Citations**: [Cloudflare Origin CA docs][cf-origin-ca]
+
+### Migration Job for schema changes
+
+**Why**: Currently every api pod runs `MigrateWithLock()` on startup,
+serializing on a Postgres advisory lock. Adds 90-240s to cold startup
+and caused bug #13 in Chapter 19.
+
+**How**: Create a Kubernetes `Job` resource that runs the api image
+with a `--migrate-only` flag. Job runs once per deploy, completes when
+schema is current. api pods get an initContainer that waits for the
+Job to complete.
+
+Requires Go code change to support `--migrate-only` flag.
+
+**Effort**: 3-4 hours (code + job manifest + testing).
+
+### Redis password
+
+**Why**: Redis runs in the cluster with no auth. Any compromised pod
+could read cache or queue state.
+
+**How**: Set `REDIS_PASSWORD` in `honeydue-secrets`, update api/worker
+env, update Redis command to include `--requirepass`. Already partially
+wired up in the manifests.
+
+**Effort**: 20 min.
+
+### Image signing with cosign
+
+**Why**: No guarantee that an image pulled from Gitea is the one we
+built. Gitea compromise = arbitrary code execution in cluster.
+
+**How**:
+1. Install cosign on build machine
+2. Sign images as part of deploy: `cosign sign gitea.treytartt.com/admin/honeydue-api:<sha>`
+3. Deploy Kyverno (or Connaisseur) to cluster
+4. Apply cluster policy requiring all images have valid cosign signatures
+
+**Effort**: 4-6 hours.
+
+### etcd encryption at rest
+
+**Why**: Kubernetes Secrets are stored in etcd unencrypted by default.
+Node disk compromise = plaintext secrets.
+
+**How**: K3s supports `--secrets-encryption` flag at server install.
+Need to recreate cluster or re-install k3s server on each node.
+
+**Effort**: 1 hour.
+
+### Automated unattended-upgrades
+
+**Why**: Currently OS patches require manual `apt upgrade`. Security
+patches can be delayed.
+
+**How**:
+```bash
+sudo apt install unattended-upgrades
+# Configure /etc/apt/apt.conf.d/50unattended-upgrades for security-only
+sudo dpkg-reconfigure -plow unattended-upgrades
+```
+
+**Effort**: 30 min per node.
+
+### fail2ban
+
+**Why**: SSH is open to the world. No rate limiting on failed attempts.
+Bot noise is constant.
+
+**How**: `sudo apt install fail2ban; sudo systemctl enable --now fail2ban`.
+Default config bans IPs after 5 failed attempts for 10 min.
+
+**Effort**: 15 min per node.
+
+### Move SSH off port 22
+
+**Why**: Port 22 attracts constant scanner noise. Moving to a
+non-default port cuts >90% of attempts.
+
+**How**:
+1. Edit `/etc/ssh/sshd_config` on each node: `Port 2222`
+2. UFW rule: `sudo ufw allow 2222/tcp`
+3. Update `~/.ssh/config` on operator: `Port 2222`
+4. Restart sshd: `sudo systemctl restart ssh`
+5. Remove UFW rule for port 22 after verifying
+
+**Effort**: 30 min (and pray).
+
+## Lower priority
+
+### Prometheus + Grafana
+
+**Why**: Historical metrics, dashboards, alerting.
+
+**How**: `kube-prometheus-stack` Helm chart. Adds ~500 MB RAM across
+cluster.
+
+**Effort**: 4-6 hours including dashboard setup.
+
+### Loki log aggregation
+
+**Why**: Cross-pod log queries, longer retention.
+
+**How**: `grafana/loki` + `promtail` DaemonSet. Integrates with existing
+Grafana.
+
+**Effort**: 2-3 hours.
+
+### OpenTelemetry tracing
+
+**Why**: Request-level profiling. Show which hop dominates p99 latency.
+
+**How**: Add OpenTelemetry SDK to Go app; export to Jaeger/Tempo.
+
+**Effort**: 8-12 hours including tuning.
+
+### Hetzner private network
+
+**Why**: Currently all inter-node traffic (including Flannel overlay)
+goes over public network. Private network = less attack surface, no
+bandwidth costs (if metered in future).
+
+**How**: Attach Hetzner vswitch to the 3 nodes, reconfigure Flannel to
+advertise private IPs, update UFW rules to allow from private IP range
+instead of specific public IPs.
+
+**Effort**: 2-3 hours including testing Flannel reconfig.
+
+### Move secrets to Vault
+
+**Why**: Kubernetes Secrets are base64-encoded etcd values. Vault is
+purpose-built for secret management with audit logs, dynamic secrets,
+rotation policies.
+
+**How**: Deploy Vault in the cluster (or external), migrate secret
+values, use Vault Agent Injector or External Secrets Operator.
+
+**Effort**: 6-8 hours.
+
+Not high priority until we have multiple engineers who shouldn't see
+every secret, or compliance requirements.
+
+### Automated backups to B2
+
+**Why**: Neon's backup is Neon's problem. If Neon-as-a-company
+disappeared, we'd lose everything.
+
+**How**: Nightly `pg_dump | gzip | aws s3 cp` (via `s3cmd` for B2) as a
+CronJob in the cluster.
+
+**Effort**: 2 hours.
+
+### Multi-region
+
+**Why**: ~100 ms CF→origin hop could be reduced by having origins in
+multiple regions. Not needed at current scale.
+
+**How**: Add 2 more Hetzner nodes in ash (Ashburn, US). Separate k3s
+cluster (or one stretched cluster — painful). Cloudflare Load Balancing
+for geo-based routing.
+
+**Effort**: Days of work, doubling cost. Don't until traffic justifies.
+
+### CF Workers for static + caching
+
+**Why**: Certain endpoints (the marketing landing page, public API
+lookups) could serve from CF Workers with near-zero origin load.
+
+**How**: Move static pages to Cloudflare Pages; cache API responses
+with `Cache-Control: public, max-age=300`.
+
+**Effort**: 4-6 hours.
+
+### WireGuard-encrypted overlay
+
+**Why**: Current Flannel VXLAN is plaintext between nodes. An attacker
+with Hetzner-internal network access could read pod-to-pod traffic.
+
+**How**: K3s supports `--flannel-backend=wireguard-native`. Reinstall
+k3s server on each node with the new backend.
+
+**Effort**: 2-3 hours (requires brief downtime).
+
+## Scaling triggers
+
+| Trigger | Action |
+|---|---|
+| p99 latency > 500ms sustained | Investigate with tracing; consider CF Workers for cached paths |
+| API CPU > 70% sustained | HPA already configured; may need more nodes |
+| DB connections at Neon limit | Upgrade Neon Scale or reduce `DB_MAX_OPEN_CONNS` |
+| Redis memory > 80% | Scale Redis memory; consider cache sharding |
+| B2 storage > 500 GB | Evaluate if R2 (free egress) is cheaper overall |
+| Active users > 100k | Evaluate multi-region, CF Pro, paid monitoring |
+| Revenue > $5k/mo | Hire ops help; this document assumes solo operator |
+
+## Known gaps we accept
+
+- **No canary deploys**: all-or-nothing rollouts via `kubectl set image`
+- **No feature flags** (app-level): code is deployed as-is. Can't toggle
+  features without re-deploying
+- **No A/B testing infra**: out of scope for current product stage
+- **No Windows/tablet-specific CDN rules**: CF serves everyone the same
+  responses
+- **No explicit blue-green**: rolling updates only
+
+## Stuff to delete when brave
+
+- `deploy/` (the Swarm era) — once we've been on k3s 30 days
+- Legacy UFW rules from the Swarm era (2377, 7946, 4789, ESP, 500, 3000)
+  — they don't hurt but they're confusing
+- `deploy-k3s/manifests/secrets.yaml.example` — we don't use this
+  pattern, we create secrets imperatively
+
+## Stuff that could go wrong and we should plan for
+
+- **Hetzner price hike**: 2026-04-01 already happened. If another one
+  comes, we could migrate to Netcup or OVH for savings.
+- **Neon EOL free tier**: Neon could change pricing policy. Fallback:
+  self-host Postgres on a Hetzner box or migrate to Supabase.
+- **Cloudflare Free plan changes**: CF could restrict Free features.
+  Fallback: BunnyCDN, or raw nodes without CDN.
+- **Gitea host outage**: If Gitea is down, deploys can't pull new
+  images. Existing pods continue. For long outages, we'd cache images
+  locally or temporarily push to Docker Hub.
+
+## Progress tracker
+
+As items are done, mark them here. Think of this as a running changelog.
+
+- [x] k3s migration from Swarm (2026-04-24)
+- [x] Traefik DaemonSet + hostNetwork
+- [x] Admin seed via ADMIN_EMAIL + ADMIN_PASSWORD
+- [x] Documentation book (this doc set)
+- [ ] All other items above