Fix: Improve file serving content-disposition and filename

Co-authored-by: aider (gemini/gemini-2.5-pro) <aider@aider.chat>

app/app.py

@@ -1383,7 +1383,12 @@ async def api_files_full(path_b64: str, request: Request):
     if not _is_safe_path(UPLOAD_ROOT, file_path) or not os.path.isfile(file_path):
         return Response(status_code=404)
 
-    return FileResponse(file_path)
+    mime_type, _ = mimetypes.guess_type(file_path)
+    disposition = "attachment"
+    if mime_type and (mime_type.startswith(('image/', 'video/', 'audio/', 'text/')) or mime_type == 'application/pdf'):
+        disposition = "inline"
+
+    return FileResponse(file_path, content_disposition_type=disposition, filename=os.path.basename(rel_path))
 
 
 @app.get("/api/files/zip/{path_b64}")