Stage 1: backend foundation (Postgres, sessions, accounts, OTel)

- internal/postgres: pgx-over-database/sql pool (otelsql), embedded goose
  migrations into schema 'backend', committed go-jet code + cmd/jetgen tool.
- internal/account: durable accounts + unified telegram/email identities
  (UUIDv7 keys), find-or-create provisioning with unique-conflict handling.
- internal/session: opaque 256-bit tokens stored as a SHA-256 hash, revoke-only
  (no TTL); write-through cache gating /readyz; store + service.
- internal/telemetry: OTel tracer/meter providers (none/stdout) + request-timing
  middleware; internal/config gains Postgres + OTel env loading.
- internal/server: /api/v1 {public,user,internal,admin} skeleton + X-User-ID
  middleware; /readyz checks DB ping + cache; main wires
  telemetry -> db+migrate -> warm cache -> server.
- Tests: unit + integration (build tag 'integration', testcontainers
  postgres:17) for migrations, accounts, sessions, readyz; new integration.yaml.
- Docs: ARCHITECTURE, TESTING, PLAN refinements, root + backend READMEs.

Session/account REST handlers deferred to Stage 6 (gateway); OTLP + dashboards
to Stage 11.

docs/TESTING.md

@@ -8,8 +8,11 @@ tests or touching CI.
 - **Go unit tests** — table-driven where it helps; `testing` + standard library.
   Every functional change ships with regression coverage. Run:
   `go test -count=1 ./backend/...` (the module list grows with the workspace).
-- **Integration** *(introduced with Postgres in Stage 1)* — `testcontainers-go`
-  spins real dependencies (Postgres). Slow; a separate CI workflow.
+- **Integration** *(Stage 1+)* — Postgres-backed tests behind the `integration`
+  build tag spin a throwaway `postgres:17-alpine` via `testcontainers-go`. They
+  live in `backend/internal/inttest` and run with
+  `go test -tags=integration -count=1 -p=1 ./backend/...` (needs Docker), guarded
+  by a separate CI workflow (`integration.yaml`; Ryuk disabled, serial). Slow.
 - **UI** *(introduced with the UI in Stage 7)* — Vitest (unit) + Playwright
   (e2e), mirroring the chosen plain-Svelte + Vite toolchain.
 - **Engine** — correctness of scoring and move generation is owned by