Retire the SQLite backend — Postgres is the only engine

The dual backend (SQLite via db.js + Postgres via schema.pg.sql) was a
maintenance foot-gun: a schema change could land on the SQLite path only and
silently 500 every read on prod (it just did, with #18/#13). Production has run
on Postgres for weeks, so SQLite is retired: ONE schema source of truth
(db/schema.pg.sql), no drift possible.

- dbx.js: default DB_BACKEND=pg; an unknown backend now fails loudly at require
  time instead of silently selecting a stale engine.
- Deleted server/db.js, server/db/sqlite.js, server/db/migrate-sqlite-to-pg.js,
  server/scripts/migrate-bizgaze-only.js (all SQLite-only, none in the runtime
  path — the running server loads db/pg.js).
- Tests (e2e, db-smoke) target Postgres now and fail-fast (skip) unless
  DATABASE_URL points at a disposable test DB — never SQLite, never prod.
- Removed the dead DB_PATH env + fixed misleading SQLite comments in the
  Dockerfile / docker-compose (kept the /data volume: it holds
  uploads/recordings/transcripts/downloads, not just the old data.db).
- CLAUDE.md: stack + repo-layout + run-locally updated for Postgres-only.

Runtime is unaffected (prod already sets DB_BACKEND=pg and pg is a prod dep);
this only removes the unused SQLite path.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

CLAUDE.md

@@ -12,8 +12,11 @@ Roadmap: grow into a communication platform (meetings + persistent chat) for
 registered BizGaze users.
 
 ## Tech stack (intentionally minimal — keep it this way)
-- **Node.js >= 22.5**, single npm dependency: `ws` (WebSocket).
-- **Built-in `node:sqlite`** (no native modules). DB file: `server/data.db`.
+- **Node.js >= 22.5**. npm deps: `ws`, `pg`, `redis`, `web-push` (+ optional `nodemailer`).
+- **PostgreSQL** via the async adapter (`server/dbx.js` → `server/db/pg.js`). SQLite was RETIRED 2026-08-12:
+  there is now ONE schema source of truth, **`server/db/schema.pg.sql`** — every schema change goes there
+  (and post-cutover COLUMNS need an explicit `ALTER TABLE … ADD COLUMN IF NOT EXISTS`, since the file is
+  applied idempotently on every boot and `CREATE TABLE IF NOT EXISTS` won't alter an existing table).
 - **WebRTC** peer-to-peer for media (screen video + voice + data channels).
 - **No build step, no framework.** Each page is a single self-contained HTML file
   with inline `<style>` and `<script>`. Do not introduce React/bundlers.
@@ -30,9 +33,10 @@ server/
   routes.js      # HTTP JSON API (/api/*, /sso) -> { "METHOD /path": handler } map
   static.js      # static file serving + authenticated recording/transcript downloads
   signaling.js   # WebSocket signaling (consent + SDP/ICE relay)
-  repos.js       # data-access layer — ALL SQL lives here (tenant-scoped)
+  repos.js       # data-access layer — ALL SQL lives here (tenant-scoped, async)
   bizgaze.js     # BizGaze identity provider (validate login, env-gated)
-  db.js          # node:sqlite schema + idempotent migrations
+  dbx.js         # async DB adapter facade -> db/pg.js (Postgres; only backend)
+  db/pg.js       # Postgres backend; db/schema.pg.sql = the single schema source of truth
   auth.js        # scrypt hashing, token/id generation, TOTP helpers
   package.json   # { "dependencies": { "ws": "^8.18" }, engines node>=22.5 }
   test/e2e.js    # 21-check backend e2e (register->login->session->signaling->audit)
@@ -48,11 +52,16 @@ server/
   transcripts/   # saved transcripts (.txt)           [created at runtime]
 ```
 Architecture/roadmap detail lives in `ARCHITECTURE.md`. Backend SQL must go through
-`repos.js` (never inline in routes/signaling). Run `node test/e2e.js` after backend edits.
+`repos.js` (never inline in routes/signaling). ANY schema change goes in `db/schema.pg.sql` (see stack note).
+After backend edits, run the tests against a DISPOSABLE Postgres (they no longer bundle SQLite):
+`DATABASE_URL=postgres://…/bizgaze_test node test/db-smoke.js`.
 
 ## Run locally
 ```
-cd server && npm install && node server.js
+# Start a local Postgres (or use the compose one), then:
+docker compose up -d bizgazepg
+cd server && npm install
+DB_BACKEND=pg DATABASE_URL=postgres://bizgaze:bizgaze_local@localhost:5432/bizgaze node server.js
 # HTTP on :8090 (HTTPS on :8443 only if cert.pem + key.pem exist in server/)
 # Env: ALLOW_REGISTRATION=1 opens the first-team registration
 ```