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- ch19: postscript on §13 noting MigrateWithLock approach is superseded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/appendices/a-glossary.md

@@ -173,11 +173,21 @@ suffix. (Chapter 8)
 ## Go + Asynq
 
 **AutoMigrate**: GORM function that syncs DB schema to Go structs.
-(Chapter 8)
+We used this in production until 2026-04, replaced by goose. Tests
+still use it via `testutil.SetupTestDB`. (Chapter 8)
 
 **Asynq**: Go library for background job queues. Redis-backed.
 (Chapter 7)
 
+**goose**: pressly/goose — the SQL migration tool we use in production
+(commit 12b2f9d onward). Migration files live in `migrations/`, one
+file per version with `-- +goose Up` / `-- +goose Down` markers.
+(Chapter 8)
+
+**goose_db_version**: goose's version-tracking table. One row per
+applied migration. `RequireSchemaApplied` reads the latest row at
+api/worker startup to fail fast on a stale schema. (Chapter 8)
+
 **GORM**: Go ORM we use. (Chapter 8)
 
 **pgx**: Go Postgres driver used by GORM. (Chapter 8)