Scaffold project and implement config, DB schema/queries

- Set up package.json (ESM, scripts), tsconfig.json, vitest.config.ts
- Install runtime and dev dependencies
- Add CLAUDE.md with architecture notes and code quality rules
- Config module with env var parsing and JWT_SECRET validation
- DB schema: users + files tables with FK cascade
- DB queries: createUser, getUserBy*, createFile, getFileById, getFilesByUserId, deleteFile
- Tests for config, db/users, db/files (15 tests passing)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

vitest.config.ts

@@ -0,0 +1,9 @@
+import { defineConfig } from 'vitest/config';
+
+export default defineConfig({
+  test: {
+    root: '.',
+    include: ['tests/**/*.test.ts'],
+    globals: true,
+  },
+});