Create REST API Endpoints for Your App

Build a set of REST API endpoints so external services and scripts can interact with this app's project data. Implement five endpoints: GET /api/projects (returns a JSON array of all projects belonging to the authenticated user), POST /api/projects (creates a new project from the request body, returns the created object with 201 status), GET /api/projects/:id (returns a single project or 404 if not found), PUT /api/projects/:id (updates the specified project's fields from the request body), and DELETE /api/projects/:id (deletes the project and returns 204). Authenticate all requests by reading an Authorization: Bearer [key] header and looking up the key in an api_keys table that links to a user_id. If the key is missing or invalid, return 401. If the user tries to access another user's project, return 403. Return consistent JSON error objects in the format { error: "message" } for all error responses.