feat: add JWT authentication with register, login, refresh, and me endpoints

Adds bcrypt password hashing, JWT access/refresh token generation, requireAuth middleware, and /api/auth routes (POST /register, POST /login, POST /refresh, GET /me).

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

pnpm-workspace.yaml

@@ -1,2 +1,5 @@
 packages:
   - "packages/*"
+
+onlyBuiltDependencies:
+  - bcrypt