db: drizzle schema matching spec 02, initial migrations, settings service

Migration 0000 enables citext; 0001 creates all 39 tables. DB tests use a
throwaway database per file (TEST_DATABASE_URL, derived from .env in dev,
a postgres service in CI). Decision 0002: pg driver and @fastify/cookie.

Task: M1-T1

pnpm-workspace.yaml

@@ -1,3 +1,7 @@
 packages:
   - apps/*
   - packages/*
+
+# esbuild (via drizzle-kit) ships prebuilt binaries; its postinstall check is not needed.
+allowBuilds:
+  esbuild: false