Drop the vestigial Postgres dependency

[AltanS]

Postgres now holds exactly one table — data_migrations, the data-migration runner's own bookkeeping ledger (drizzle/schema.ts). All personal data left the server in M117/03 (tracker data → browser IndexedDB) and M128/03 (account system removed); the E2EE sync tables live in openplate-sync. The server stores no user data at all.

Yet a self-hoster still has to run a full Postgres 17 container so a migration runner can record which migrations ran — on a database with nothing left to migrate.

Proposed: remove the Postgres dependency entirely — drop drizzle/the pool/data_migrations, the compose postgres service, the DB_* env vars, and the migration step in scripts/start.sh. Any future one-shot data transforms would be client-side (IndexedDB schema versioning already handles this in app/lib/local-store/).

Payoff: the self-host story becomes a single stateless container, matching what the README promises (local-first, no server data).

Care needed: the hosted deploy's existing data_migrations rows and Bay config reference the DB; removal must land as a coordinated deploy.

[AltanS]

Done — the app is now a single stateless container with no database.

Removed: drizzle/ in full (schema, 9 SQL migrations + meta, db.ts pool, pool-retry.ts, the data-migration runner and its two migration files), drizzle.config.ts, the whole cli/ tree (its only command groups were db and data-migration), the migrate + data-migration steps from scripts/start.sh, the pool init/close from server.ts, CONFIG.database, the dead app/lib/numeric.ts (existed only for Drizzle numeric columns), and the deps drizzle-orm/drizzle-kit/pg/@types/pg/commander/cli-table3 plus the drizzle:* and cli scripts.

Config/compose: DB_* gone from .env.example and both compose files; docker-compose.yml is now one app service with no postgres and no volume; docker-compose.full.yml keeps Postgres for openplate-sync only — the app's depends_on/DB_* are gone and the two-database init-script hack was dropped (POSTGRES_DB is now the sync DB directly).

drizzle/types/enums.ts was pure TS with no DB dependency — moved to types/enums.ts (#drizzle/* alias removed from tsconfig).

Docs: README, AGENTS.md, CONTRIBUTING.md updated (the "what Postgres holds" note is replaced with the simpler truth — no database, nothing to back up on the server, one-container quickstart); ADR-0002 marked Superseded, ADR-0006 carries an update note.

Gates: lint 0 warnings, typecheck clean, unit 1909/1909 (1919 − the 10 pool-retry tests, the only tests of removed code), production build OK, clean pnpm install --frozen-lockfile OK, and a boot smoke with no DB env in the environment returned 200 from /healthcheck. Shipped as e8feb59 / v0.1.0; both Release Image runs green and ghcr.io/lowcarbcheck/openplate:latest is on the new commit.