feat(api): implement FastAPI routes with JWT authentication

- jokes.py: Public joke listing, detail, and random endpoints
- categories.py: Type and crowd listing endpoints
- auth.py: Login endpoint with JWT token generation
- admin.py: Full CRUD for jokes, types, crowds with JWT protection
- Fix request body schemas to use Create DTOs instead of Response models

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

api/app/routers/__init__.py

@@ -0,0 +1,6 @@
+from .jokes import router as jokes_router
+from .categories import router as categories_router
+from .auth import router as auth_router
+from .admin import router as admin_router
+
+__all__ = ["jokes_router", "categories_router", "auth_router", "admin_router"]