docs(deployment): rewrite migration prose for goose adoption

Update the deployment book and glossary to reflect the goose-based
schema migration flow shipped in 12b2f9d/0f7450a:

- ch07: clarify startup probe assumes migrations ran out-of-band
- ch08: drop AutoMigrate-with-advisory-lock prose; describe goose Job
- ch12: pod startup checks goose_db_version, no longer runs migrations
- ch14: document the Job→wait→roll deploy gate and how to debug failures
- ch16: add "Migrate Job fails during deploy" + "Schema precondition
  failed" failure modes
- ch17: new runbook entries §26 (run migrations manually), §27 (recover
  from failed/dirty migration), §28 (bootstrap goose on fresh clone)
- ch19: postscript on §13 noting MigrateWithLock approach is superseded
- ch20: mark "Migration Job for schema changes" task done
- glossary: add `goose` and `goose_db_version`; flag AutoMigrate as
  tests-only
- references: add goose links; flag AutoMigrate as tests-only

docs/deployment/12-data-flow.md

@@ -272,7 +272,7 @@ sequenceDiagram
     participant NewPod as api pod v2 (starting)
 
     Note over NewPod: kubelet starts new pod
-    Note over NewPod: pod connects to Postgres<br/>MigrateWithLock runs (no-op)<br/>HTTP server starts<br/>readinessProbe passes
+    Note over NewPod: pod connects to Postgres<br/>RequireSchemaApplied checks goose_db_version<br/>HTTP server starts<br/>readinessProbe passes
     Note over NewPod: kube-proxy updates endpoints<br/>NewPod added to Service pool
     CF->>Traefik: request 1
     Traefik->>OldPod: routed (old pod still in pool)