feat: Initialize FastAPI AI Gateway project structure with authentication, module management, and LLM API routing.

app/api/deps.py

@@ -0,0 +1,43 @@
+from fastapi import Security, HTTPException, status, Depends
+from fastapi.security.api_key import APIKeyHeader
+from sqlalchemy.orm import Session
+from app.core.config import settings
+from app.core.database import get_db
+from app.models.module import Module
+from cachetools import TTLCache
+
+api_key_header = APIKeyHeader(name="X-API-Key", auto_error=False)
+
+# Cache keys for 5 minutes, store up to 1000 keys
+# This prevents a Supabase round-trip on every message
+auth_cache = TTLCache(maxsize=1000, ttl=300)
+
+async def get_api_key(
+    api_key_header: str = Security(api_key_header),
+    db: Session = Depends(get_db)
+):
+    if not api_key_header:
+        raise HTTPException(
+            status_code=status.HTTP_403_FORBIDDEN, 
+            detail="API Key missing"
+        )
+
+    # 1. Fallback to global static key (Admin)
+    if api_key_header == settings.API_KEY:
+        return api_key_header
+    
+    # 2. Check Cache first (VERY FAST)
+    if api_key_header in auth_cache:
+        return api_key_header
+    
+    # 3. Check Database for Module key (Database round-trip)
+    module = db.query(Module).filter(Module.secret_key == api_key_header, Module.is_active == True).first()
+    if module:
+        # Save to cache for next time
+        auth_cache[api_key_header] = True
+        return api_key_header
+
+    raise HTTPException(
+        status_code=status.HTTP_403_FORBIDDEN, 
+        detail="Could not validate credentials or API Key is inactive"
+    )