feat(db): add PostgreSQL connection, migration runner, and seed data

- Add pool export and graceful shutdown hook to db/index.ts
- Create migrate.ts — programmatic migration runner using drizzle-orm/migrator
- Create seed.ts — idempotent seed script with sample users, subscriptions,
  watchlist items, exposures, alerts, blog posts, properties, and removal requests
- Create db.test.ts — unit tests for db, migrate, and seed module exports
- Add web/.env.example documenting DATABASE_URL
- Add db:generate, db:push, db:migrate, db:seed scripts to web/package.json

pnpm-lock.yaml

@@ -80,6 +80,9 @@ importers:
       jsdom:
         specifier: ^29.1.1
         version: 29.1.1
+      tsx:
+        specifier: ^4.22.3
+        version: 4.22.3
       vite-plugin-solid:
         specifier: ^2.11.12
         version: 2.11.12(solid-js@1.9.13)(vite@7.3.3(@types/node@25.9.1)(jiti@2.7.0)(lightningcss@1.32.0)(terser@5.48.0))