fix(db): bootstrap migrations on local-tier gateway startup

Fresh `mosaic gateway install` (npm) left the gateway DB schema empty —
sign-in 500'd with `relation "users" does not exist`, and every entry
point (auth, bootstrap setup) failed because they all query the users
table first. Five stacked bugs on the local (PGlite) tier:

1. `packages/db/package.json` `files: ["dist"]` excluded the `drizzle/`
   SQL migrations from the published tarball.
2. `runMigrations()` only supports postgres-js — unusable for embedded
   PGlite.
3. `apps/gateway/src/database/database.module.ts` never invoked
   migrations at startup.
4. `createPgliteDb` didn't load pgvector, so migration 0001's
   `CREATE EXTENSION vector` failed.
5. Drizzle's PG migrator wraps every migration in one outer
   transaction, which trips Postgres' `check_safe_enum_use` on
   migration 0009 (`ALTER TYPE ADD VALUE 'pending'` → `SET DEFAULT
   'pending'` in the same tx).

Changes:
- Ship `drizzle/` in the published tarball.
- `createPgliteDb` loads `@electric-sql/pglite/vector`.
- New `runPgliteMigrations(handle)` walks the Drizzle journal and
  runs each statement-breakpoint chunk through PGlite's `client.exec()`
  (autocommit per statement). Records into `drizzle.__drizzle_migrations`
  for interop with the postgres-js path. Per-statement try/catch
  surfaces which statement of which migration failed.
- `DatabaseModule` runs migrations in `OnModuleInit` before
  `app.listen()`. Local tier: explicit `runPgliteMigrations` then
  `storageAdapter.migrate()`. Postgres tier: just `storageAdapter.migrate()`,
  which already calls `runMigrations(url)` internally — no double-call.
- Removed `packages/storage/src/test-utils/pglite-with-vector.ts`. The
  "intentionally not exported" rationale is moot now that migration
  0001 forces pgvector load anyway. The integration test uses
  `createPgliteDb` + `runPgliteMigrations` from `@mosaicstack/db`.

Tests: BetterAuth tables exist after migrate; idempotent (re-runs 0009);
partial-failure surfaces statement-level context and leaves no ledger row.

QA on a fresh PGlite install:
- `Applying PGlite schema migrations...` then `Initializing storage
  adapter (pglite)...` in startup log.
- `GET /api/bootstrap/status` → `{"needsSetup":true}` HTTP 200 (was 500).
- `POST /api/bootstrap/setup` reaches Zod validator (was 500).

Scope: this PR fixes the local (PGlite) tier. Postgres-tier first
install still has the outer-transaction problem and a journal ordering
bug (0009's `when` < 0008's). Documented inline as TODO and in the
scratchpad — needs a separate change with real-Postgres validation.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/db/package.json

@@ -42,6 +42,7 @@
     "access": "public"
   },
   "files": [
-    "dist"
+    "dist",
+    "drizzle"
   ]
 }