fix: resolve MongoDB collection boolean check errors

- Fix NotImplementedError when checking collection objects with bool()
- Change 'if collection:' to 'if collection is not None:'
- Fixes upload endpoint 500 errors on Hugging Face Spaces
- All MongoDB operations now work correctly

server.py

@@ -138,7 +138,7 @@ async def upload_image(image: UploadFile = File(...)):
     with open(path, "wb") as f:
         f.write(contents)
     # Save metadata to Mongo
-    if uploads_col:
+    if uploads_col is not None:
         try:
             uploads_col.insert_one({"_id": image_id, "filename": os.path.basename(path), "path": path})
         except Exception:
@@ -198,7 +198,7 @@ def get_hairswap(req: HairSwapRequest):
             out_img.save(out_path)
             LOGGER.info(f"Result saved: {out_path}")
             
-            if results_col:
+            if results_col is not None:
                 try:
                     results_col.insert_one({
                         "_id": result_id,
@@ -236,7 +236,7 @@ def logs(limit: int = 50, level: str = None, logger_name: str = None):
     response_data = {}
     
     # Get metadata (uploads and results)
-    if uploads_col and results_col:
+    if uploads_col is not None and results_col is not None:
         uploads = list(uploads_col.find({}, {"_id": 1, "filename": 1}).limit(20))
         results = list(results_col.find({}, {"_id": 1, "filename": 1, "source_id": 1, "reference_id": 1}).limit(20))
         response_data["metadata"] = {"uploads": uploads, "results": results}