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>

CLAUDE.md

@@ -0,0 +1,28 @@
+# Nanodrop
+
+Simple file-sharing platform. TypeScript + Fastify + SQLite.
+
+## Commands
+
+- `npm test` — Run all tests (vitest)
+- `npm run dev` — Start dev server (tsx)
+- `npm run build` — Compile TypeScript
+- `npm run register-user -- --username <user> --password <pass>` — Create user
+
+## Architecture
+
+- ESM throughout (`"type": "module"`)
+- Fastify with server-rendered HTML pages
+- SQLite via better-sqlite3 for persistence
+- JWT in httpOnly cookies for auth
+- PRG pattern for HTML forms (no client-side JS except copy-to-clipboard)
+- Dependency injection — DB/service functions take deps as params for testability
+
+## Code Quality
+
+- Review code after every change. Refactor for readability.
+- Use TDD: write tests first, then implement.
+- Build and test after every change.
+- Break large functions into smaller ones, extract duplicate code.
+- Search for duplicated code in tests and extract into reusable helpers.
+- Commit after every logical set of changes. Keep commits small and focused.