Fix 113 hardening issues across entire Go backend

Security:
- Replace all binding: tags with validate: + c.Validate() in admin handlers
- Add rate limiting to auth endpoints (login, register, password reset)
- Add security headers (HSTS, XSS protection, nosniff, frame options)
- Wire Google Pub/Sub token verification into webhook handler
- Replace ParseUnverified with proper OIDC/JWKS key verification
- Verify inner Apple JWS signatures in webhook handler
- Add io.LimitReader (1MB) to all webhook body reads
- Add ownership verification to file deletion
- Move hardcoded admin credentials to env vars
- Add uniqueIndex to User.Email
- Hide ConfirmationCode from JSON serialization
- Mask confirmation codes in admin responses
- Use http.DetectContentType for upload validation
- Fix path traversal in storage service
- Replace os.Getenv with Viper in stripe service
- Sanitize Redis URLs before logging
- Separate DEBUG_FIXED_CODES from DEBUG flag
- Reject weak SECRET_KEY in production
- Add host check on /_next/* proxy routes
- Use explicit localhost CORS origins in debug mode
- Replace err.Error() with generic messages in all admin error responses

Critical fixes:
- Rewrite FCM to HTTP v1 API with OAuth 2.0 service account auth
- Fix user_customuser -> auth_user table names in raw SQL
- Fix dashboard verified query to use UserProfile model
- Add escapeLikeWildcards() to prevent SQL wildcard injection

Bug fixes:
- Add bounds checks for days/expiring_soon query params (1-3650)
- Add receipt_data/transaction_id empty-check to RestoreSubscription
- Change Active bool -> *bool in device handler
- Check all unchecked GORM/FindByIDWithProfile errors
- Add validation for notification hour fields (0-23)
- Add max=10000 validation on task description updates

Transactions & data integrity:
- Wrap registration flow in transaction
- Wrap QuickComplete in transaction
- Move image creation inside completion transaction
- Wrap SetSpecialties in transaction
- Wrap GetOrCreateToken in transaction
- Wrap completion+image deletion in transaction

Performance:
- Batch completion summaries (2 queries vs 2N)
- Reuse single http.Client in IAP validation
- Cache dashboard counts (30s TTL)
- Batch COUNT queries in admin user list
- Add Limit(500) to document queries
- Add reminder_stage+due_date filters to reminder queries
- Parse AllowedTypes once at init
- In-memory user cache in auth middleware (30s TTL)
- Timezone change detection cache
- Optimize P95 with per-endpoint sorted buffers
- Replace crypto/md5 with hash/fnv for ETags

Code quality:
- Add sync.Once to all monitoring Stop()/Close() methods
- Replace 8 fmt.Printf with zerolog in auth service
- Log previously discarded errors
- Standardize delete response shapes
- Route hardcoded English through i18n
- Remove FileURL from DocumentResponse (keep MediaURL only)
- Thread user timezone through kanban board responses
- Initialize empty slices to prevent null JSON
- Extract shared field map for task Update/UpdateTx
- Delete unused SoftDeleteModel, min(), formatCron, legacy handlers

Worker & jobs:
- Wire Asynq email infrastructure into worker
- Register HandleReminderLogCleanup with daily 3AM cron
- Use per-user timezone in HandleSmartReminder
- Replace direct DB queries with repository calls
- Delete legacy reminder handlers (~200 lines)
- Delete unused task type constants

Dependencies:
- Replace archived jung-kurt/gofpdf with go-pdf/fpdf
- Replace unmaintained gomail.v2 with wneessen/go-mail
- Add TODO for Echo jwt v3 transitive dep removal

Test infrastructure:
- Fix MakeRequest/SeedLookupData error handling
- Replace os.Exit(0) with t.Skip() in scope/consistency tests
- Add 11 new FCM v1 tests

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

go.mod

@@ -3,12 +3,12 @@ module github.com/treytartt/honeydue-api
 go 1.24.0
 
 require (
+	github.com/go-pdf/fpdf v0.9.0
 	github.com/go-playground/validator/v10 v10.23.0
 	github.com/golang-jwt/jwt/v5 v5.3.0
 	github.com/google/uuid v1.6.0
 	github.com/gorilla/websocket v1.5.3
 	github.com/hibiken/asynq v0.25.1
-	github.com/jung-kurt/gofpdf v1.16.2
 	github.com/labstack/echo/v4 v4.11.4
 	github.com/nicksnyder/go-i18n/v2 v2.6.0
 	github.com/redis/go-redis/v9 v9.17.1
@@ -18,11 +18,14 @@ require (
 	github.com/sideshow/apns2 v0.25.0
 	github.com/spf13/viper v1.20.1
 	github.com/stretchr/testify v1.11.1
+	github.com/stripe/stripe-go/v81 v81.4.0
+	github.com/wneessen/go-mail v0.7.2
 	golang.org/x/crypto v0.45.0
 	golang.org/x/oauth2 v0.34.0
 	golang.org/x/text v0.31.0
+	golang.org/x/time v0.14.0
 	google.golang.org/api v0.257.0
-	gopkg.in/gomail.v2 v2.0.0-20160411212932-81ebce5c23df
+	gopkg.in/yaml.v3 v3.0.1
 	gorm.io/driver/postgres v1.6.0
 	gorm.io/driver/sqlite v1.6.0
 	gorm.io/gorm v1.31.1
@@ -44,7 +47,7 @@ require (
 	github.com/go-playground/locales v0.14.1 // indirect
 	github.com/go-playground/universal-translator v0.18.1 // indirect
 	github.com/go-viper/mapstructure/v2 v2.4.0 // indirect
-	github.com/golang-jwt/jwt v3.2.2+incompatible // indirect
+	github.com/golang-jwt/jwt v3.2.2+incompatible // indirect; TODO(S-19): Pulled by echo/v4 middleware — upgrade Echo to v4.12+ which removes built-in JWT middleware (uses echo-jwt/v4 with jwt/v5 instead), eliminating this vulnerable transitive dep
 	github.com/golang-jwt/jwt/v4 v4.5.2 // indirect
 	github.com/google/s2a-go v0.1.9 // indirect
 	github.com/googleapis/enterprise-certificate-proxy v0.3.7 // indirect
@@ -71,7 +74,6 @@ require (
 	github.com/spf13/afero v1.14.0 // indirect
 	github.com/spf13/cast v1.10.0 // indirect
 	github.com/spf13/pflag v1.0.10 // indirect
-	github.com/stripe/stripe-go/v81 v81.4.0 // indirect
 	github.com/subosito/gotenv v1.6.0 // indirect
 	github.com/tklauser/go-sysconf v0.3.12 // indirect
 	github.com/tklauser/numcpus v0.6.1 // indirect
@@ -86,10 +88,7 @@ require (
 	golang.org/x/net v0.47.0 // indirect
 	golang.org/x/sync v0.18.0 // indirect
 	golang.org/x/sys v0.38.0 // indirect
-	golang.org/x/time v0.14.0 // indirect
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20251124214823-79d6a2a48846 // indirect
 	google.golang.org/grpc v1.77.0 // indirect
 	google.golang.org/protobuf v1.36.10 // indirect
-	gopkg.in/alexcesaro/quotedprintable.v3 v3.0.0-20150716171945-2caba252f4dc // indirect
-	gopkg.in/yaml.v3 v3.0.1 // indirect
 )