docs(03-02): complete wire postgresql support plan

- Add 03-02-SUMMARY.md with execution results
- Update STATE.md: advance plan, record metrics, add decisions, update session
- Update ROADMAP.md: phase 03 complete (2/2 plans, all summaries present)
- Update REQUIREMENTS.md: mark DB-02 complete

.planning/REQUIREMENTS.md

@@ -23,7 +23,7 @@ Requirements for this milestone. Each maps to roadmap phases.
 ### Database
 
 - [x] **DB-01**: PostgreSQL is supported as an alternative to SQLite via pgx v5 driver
-- [ ] **DB-02**: Database backend is selected via DATABASE_URL env var (present = PostgreSQL, absent = SQLite with DB_PATH)
+- [x] **DB-02**: Database backend is selected via DATABASE_URL env var (present = PostgreSQL, absent = SQLite with DB_PATH)
 - [x] **DB-03**: Existing SQLite users can upgrade without data loss (baseline migration represents current schema)
 
 ### Bulk Actions
@@ -99,7 +99,7 @@ Which phases cover which requirements. Updated during roadmap creation.
 | REFAC-02 | Phase 2 | Complete |
 | REFAC-03 | Phase 2 | Complete |
 | DB-01 | Phase 3 | Complete |
-| DB-02 | Phase 3 | Pending |
+| DB-02 | Phase 3 | Complete |
 | DB-03 | Phase 3 | Complete |
 | BULK-01 | Phase 4 | Pending |
 | BULK-02 | Phase 4 | Pending |

.planning/ROADMAP.md

@@ -62,7 +62,7 @@ Plans:
 
 Plans:
 - [x] 03-01-PLAN.md — Create PostgresStore (9 Store methods), PostgreSQL migration files, rename RunMigrations to RunSQLiteMigrations, add RunPostgresMigrations
-- [ ] 03-02-PLAN.md — Wire DATABASE_URL branching in main.go, fix cross-dialect UNIQUE detection, add Docker Compose postgres profiles, create build-tagged test helper
+- [x] 03-02-PLAN.md — Wire DATABASE_URL branching in main.go, fix cross-dialect UNIQUE detection, add Docker Compose postgres profiles, create build-tagged test helper
 
 ### Phase 4: UX Improvements
 **Goal**: Users can manage a large list of updates efficiently — dismissing many at once, finding specific images quickly, and seeing new arrivals without manual refreshes

.planning/STATE.md

@@ -2,14 +2,14 @@
 gsd_state_version: 1.0
 milestone: v1.0
 milestone_name: milestone
-status: Ready to execute
+status: Phase complete — ready for verification
-stopped_at: Completed 03-01-PLAN.md
+stopped_at: Completed 03-02-PLAN.md
-last_updated: "2026-03-24T08:10:37.889Z"
+last_updated: "2026-03-24T08:14:20.006Z"
 progress:
   total_phases: 4
-  completed_phases: 2
+  completed_phases: 3
   total_plans: 6
-  completed_plans: 5
+  completed_plans: 6
 ---
 
 # Project State
@@ -51,6 +51,7 @@ Plan: 2 of 2
 | Phase 02-backend-refactor P01 | 7min | 2 tasks | 7 files |
 | Phase 02-backend-refactor P02 | 3min | 2 tasks | 4 files |
 | Phase 03-postgresql-support P01 | 3min | 2 tasks | 7 files |
+| Phase 03-postgresql-support P02 | 2min | 2 tasks | 5 files |
 
 ## Accumulated Context
 
@@ -73,6 +74,9 @@ Recent decisions affecting current work:
 - [Phase 02-backend-refactor]: NewTestServer pattern: each test gets its own in-memory SQLite DB (RunMigrations + NewSQLiteStore + NewServer) - eliminates shared global state between tests
 - [Phase 03-postgresql-support]: PostgresStore uses *sql.DB via pgx/v5/stdlib adapter with no mutex; TEXT timestamps match SQLiteStore scan logic
 - [Phase 03-postgresql-support]: CreateTag uses RETURNING id in PostgresStore (pgx does not support LastInsertId); AssignTag uses ON CONFLICT DO UPDATE
+- [Phase 03-postgresql-support]: DATABASE_URL presence-check activates PostgreSQL; absent falls back to SQLite — simpler UX than a separate DB_DRIVER var
+- [Phase 03-postgresql-support]: postgres Docker service uses profiles: [postgres] with required: false depends_on — default compose up unchanged, SQLite only
+- [Phase 03-postgresql-support]: UNIQUE constraint detection uses strings.ToLower for case-insensitive matching across SQLite (uppercase UNIQUE) and PostgreSQL (lowercase unique)
 
 ### Pending Todos
 
@@ -85,6 +89,6 @@ None yet.
 
 ## Session Continuity
 
-Last session: 2026-03-24T08:10:37.887Z
+Last session: 2026-03-24T08:14:20.004Z
-Stopped at: Completed 03-01-PLAN.md
+Stopped at: Completed 03-02-PLAN.md
 Resume file: None

.planning/phases/03-postgresql-support/03-02-SUMMARY.md

@@ -0,0 +1,88 @@
+---
+phase: 03-postgresql-support
+plan: "02"
+subsystem: wiring
+tags: [postgresql, sqlite, database, docker-compose, branching]
+dependency_graph:
+  requires: [03-01]
+  provides: [DATABASE_URL branching, postgres docker profile, NewTestPostgresServer]
+  affects: [cmd/diunwebhook/main.go, compose.yml, compose.dev.yml, pkg/diunwebhook/diunwebhook.go]
+tech_stack:
+  added: []
+  patterns: [DATABASE_URL env var branching, Docker Compose profiles, build-tagged test helpers]
+key_files:
+  created:
+    - pkg/diunwebhook/postgres_test.go
+  modified:
+    - cmd/diunwebhook/main.go
+    - pkg/diunwebhook/diunwebhook.go
+    - compose.yml
+    - compose.dev.yml
+decisions:
+  - "DATABASE_URL present activates PostgreSQL path; absent falls back to SQLite with DB_PATH"
+  - "postgres Docker service uses profiles: [postgres] so default compose up remains SQLite-only"
+  - "UNIQUE detection uses strings.ToLower for case-insensitive matching across SQLite and PostgreSQL"
+  - "Build tag //go:build postgres gates postgres_test.go so standard test runs have no pgx dependency"
+metrics:
+  duration: "~2 minutes"
+  completed: "2026-03-24T08:13:21Z"
+  tasks_completed: 2
+  files_changed: 5
+---
+
+# Phase 03 Plan 02: Wire PostgreSQL Support and Deployment Infrastructure Summary
+
+DATABASE_URL branching in main.go routes to PostgresStore or SQLiteStore at startup; Docker Compose postgres profile enables optional PostgreSQL; build-tagged test helper and cross-dialect UNIQUE detection complete the integration.
+
+## What Was Built
+
+### Updated main.go (cmd/diunwebhook/main.go)
+- `DATABASE_URL` env var check: when set, opens pgx connection, runs `RunPostgresMigrations`, creates `NewPostgresStore`, logs `"Using PostgreSQL database"`
+- When absent: existing SQLite path using `RunSQLiteMigrations` (renamed in Plan 01), `NewSQLiteStore`, logs `"Using SQLite database at {path}"`
+- Blank import `_ "github.com/jackc/pgx/v5/stdlib"` registers the `"pgx"` driver name
+- All route wiring and graceful shutdown logic unchanged
+
+### Cross-dialect UNIQUE detection (pkg/diunwebhook/diunwebhook.go)
+- `TagsHandler` now uses `strings.Contains(strings.ToLower(err.Error()), "unique")` for 409 Conflict detection
+- SQLite errors: `UNIQUE constraint failed: tags.name` (uppercase UNIQUE)
+- PostgreSQL errors: `duplicate key value violates unique constraint "tags_name_key"` (lowercase unique)
+- Both backends now return 409 correctly
+
+### Docker Compose postgres profiles
+- `compose.yml`: postgres service added with `profiles: [postgres]`, healthcheck via `pg_isready`, `DATABASE_URL` env var in app service, conditional `depends_on` with `required: false`, `postgres-data` volume
+- `compose.dev.yml`: same postgres service with port 5432 exposed on host for direct psql access during development
+- Default `docker compose up` (no profile) unchanged — SQLite only, no new services start
+
+### Build-tagged test helper (pkg/diunwebhook/postgres_test.go)
+- `//go:build postgres` tag — only compiled with `go test -tags postgres`
+- `NewTestPostgresServer()` constructs a `*Server` backed by PostgreSQL using `TEST_DATABASE_URL` env var (defaults to `postgres://diun:diun@localhost:5432/diundashboard_test?sslmode=disable`)
+- Calls `RunPostgresMigrations` and `NewPostgresStore` — mirrors the production startup path
+
+## Decisions Made
+
+| Decision | Rationale |
+|----------|-----------|
+| DATABASE_URL presence-check (not a separate DB_DRIVER var) | Simpler UX; empty string = SQLite, any value = PostgreSQL |
+| profiles: [postgres] in compose files | Standard Docker Compose pattern for optional services; default deploy unchanged |
+| required: false in depends_on | App can start without postgres service (SQLite fallback); Docker Compose v2.20+ required |
+| //go:build postgres tag on test helper | Prevents pgx import at test time for standard `go test ./...` runs; explicit opt-in |
+| strings.ToLower for UNIQUE check | SQLite and PostgreSQL use different cases in constraint error messages |
+
+## Deviations from Plan
+
+None — plan executed exactly as written. The `export_test.go` rename (RunMigrations -> RunSQLiteMigrations) was already completed as a deviation in Plan 01, as noted in the objective.
+
+## Verification Results
+
+- `go build ./...` exits 0
+- `go test -count=1 ./pkg/diunwebhook/` passes (all 20+ SQLite tests, postgres_test.go skipped)
+- `docker compose config` validates without errors
+- `docker compose --profile postgres config` shows postgres service
+- `grep -c "DATABASE_URL" cmd/diunwebhook/main.go` returns 1
+- `grep "strings.ToLower" pkg/diunwebhook/diunwebhook.go` shows case-insensitive UNIQUE check
+
+## Known Stubs
+
+None — this plan wires implementation code, no UI stubs.
+
+## Self-Check: PASSED