Fix: Make pdf_source_path optional in config

- pdf_source_path is not needed for API server operation
- This was causing 503 errors because Render.com didn't have this env var
- Changed from required field to Optional[str] = None

utils/config.py

@@ -18,7 +18,7 @@ class Settings(BaseSettings):
     collection_name: str = "financial_papers"
 
     # PDF Processing Settings
-    pdf_source_path: str
+    pdf_source_path: Optional[str] = None
     chunk_size: int = 1000
     chunk_overlap: int = 200