feat: init api module with Flask app and user routes

routes/users.py

@@ -0,0 +1,10 @@
+from flask import jsonify
+
+def register_routes(app):
+    @app.route('/api/users')
+    def list_users():
+        return jsonify({'users': []})
+    
+    @app.route('/api/users/<int:user_id>')
+    def get_user(user_id):
+        return jsonify({'id': user_id, 'name': 'Alice'})