fix(05): cloud API path param, root sentinel, webdav creds in list, upload path

cloud.py: list_connections now decrypts and surfaces server_url +
connection_username for nextcloud/webdav providers; folder route uses
{folder_id:path} to handle slashes; translates "root" sentinel to "".
nextcloud_backend.py: skip parent directory entry in PROPFIND Depth:1 results.
webdav_backend.py: add cloud_folder + original_filename params to
upload_object so files land in the user's chosen folder with their real name.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/storage/nextcloud_backend.py

@@ -93,11 +93,15 @@ class NextcloudBackend(WebDAVBackend):
         # client.list() returns a list of file/folder names in the directory
         items = await asyncio.to_thread(self._client.list, folder_path)
 
+        folder_norm = folder_path.strip("/")
         result: list[dict] = []
         for name in items:
-            # Skip the "." self-reference that some WebDAV servers include
+            # Skip the "." self-reference and empty entries
             if not name or name in (".", "./"):
                 continue
+            # Skip the directory itself (PROPFIND Depth:1 always includes the parent)
+            if name.strip("/") == folder_norm:
+                continue
 
             # Construct the full path for info lookup
             if folder_path: