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.

PLAN.md

@@ -150,3 +150,26 @@ Open details: deployment target/host; dashboards; load expectations.
   compose deferred to a stage that has something to deploy. Trunk is `master`
   (owner preference); `feature/*` + PR from Stage 1; the genesis commit lands on
   `master` by necessity.
+- **Stage 1** (interview + implementation):
+  - Query layer: **go-jet** over `database/sql` (pgx stdlib) + otelsql; a
+    `cmd/jetgen` tool regenerates the **committed** code from a throwaway
+    container. Postgres **17** pinned for jetgen, tests and prod.
+  - Sessions: opaque token stored only as a **SHA-256 hash** (kept as hex
+    `text`, not `bytea` — avoids jet bytea-literal friction), **revoke-only**
+    (no TTL); revocation-audit table deferred. Backend keeps a warmed
+    write-through session cache that gates `/readyz`.
+  - Data model: **UUIDv7** PKs; one unified `identities` table
+    (`kind ∈ telegram|email`, widen to `vk`/`max` later); no soft-delete /
+    actor-audit columns yet.
+  - HTTP surface: **service/store/cache layer only**. `/api/v1/{public,user,
+    internal,admin}` groups + `X-User-ID` middleware are scaffolding (exposed via
+    `Server` group accessors); the session/account REST handlers land with the
+    gateway in **Stage 6**. Admin bootstrap deferred to **Stage 9**.
+  - Telemetry: providers + request-timing middleware + otelsql; exporters
+    `none` (default) / `stdout`; OTLP + dashboards deferred to **Stage 11**.
+  - Tests/CI: integration tests behind the `integration` build tag in
+    `backend/internal/inttest` + new `integration.yaml` (testcontainers, Ryuk
+    off, serial), firing on push and PR. Backend now **hard-depends on Postgres
+    at boot** (migrations at startup) — a deliberate contract change from
+    Stage 0, documented in both READMEs. All code stays in the existing
+    `backend` module under `internal/` (+ `cmd/jetgen`); `go.work` untouched.