fix(imports): correct RateLimitTier import and add temporary tier function

- Import RateLimitTier from infrastructure.rate_limiter where it's defined
- Add temporary get_rate_limit_tier function returning BASIC tier
- Remove non-existent import from rate_limiting middleware

src/api/routes/agents.py

@@ -13,7 +13,12 @@ from pydantic import BaseModel, Field
 from src.core import get_logger
 from src.api.middleware.authentication import get_current_user
 from src.api.auth import User
-from src.api.middleware.rate_limiting import RateLimitTier, get_rate_limit_tier
+from src.infrastructure.rate_limiter import RateLimitTier
+
+# Temporary function until proper rate limit tier detection is implemented
+async def get_rate_limit_tier() -> RateLimitTier:
+    """Get rate limit tier for current user."""
+    return RateLimitTier.BASIC
 from src.agents import ZumbiAgent, AnitaAgent, TiradentesAgent, BonifacioAgent, AgentContext
 from src.infrastructure.observability.metrics import track_time, count_calls