Fix authentication for Jellyfin 10.12 and false success reports

- Use the standard "Authorization: MediaBrowser ..., Token=..." header
  instead of the legacy X-Emby-Authorization / X-Emby-Token headers,
  which are no longer accepted by Jellyfin 10.12.
- _make_request now returns True on empty successful responses (204)
  and None only on errors, so failed tag updates are reported as failures.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tag_artist.py

@@ -51,15 +51,23 @@ class JellyfinTagger:
         self.user_id = None
         self.access_token = None
         
-        # Set up headers
+        # Set up headers (Jellyfin 10.12+ only accepts the standard Authorization header,
+        # the legacy X-Emby-* headers are no longer supported)
         self.session.headers.update({
             'Content-Type': 'application/json',
-            'X-Emby-Authorization': 'MediaBrowser Client="SimpleTagger", Device="Python Script", DeviceId="simple-tagger", Version="1.0.0"'
+            'Authorization': self._auth_header()
         })
         
         # Authenticate
         self._authenticate()
-    
+
+    def _auth_header(self) -> str:
+        """Build the MediaBrowser Authorization header, including the token once authenticated."""
+        header = 'MediaBrowser Client="SimpleTagger", Device="Python Script", DeviceId="simple-tagger", Version="1.0.0"'
+        if self.access_token:
+            header += f', Token="{self.access_token}"'
+        return header
+
     def _authenticate(self):
         """Authenticate with Jellyfin using username and password."""
         auth_url = f"{self.server_url}/Users/AuthenticateByName"
@@ -78,7 +86,7 @@ class JellyfinTagger:
             
             # Update headers with access token
             self.session.headers.update({
-                'X-Emby-Token': self.access_token
+                'Authorization': self._auth_header()
             })
             
         except requests.exceptions.RequestException as e:
@@ -95,7 +103,8 @@ class JellyfinTagger:
             
             if response.content:
                 return response.json()
-            return None
+            # Success without body (e.g. 204 No Content); None is reserved for errors
+            return True
             
         except requests.exceptions.HTTPError as e:
             print(f"❌ HTTP error {e.response.status_code}: {e}")
@@ -192,8 +201,8 @@ class JellyfinTagger:
                                     json=update_data, 
                                     params=update_params)
         
-        # Consider it successful if we get any response (including 204 No Content)
-        return result is not False
+        # _make_request returns None on any error, True on 204 No Content
+        return result is not None
 
 
 def main():