The 'tag' extra field is required in Spoolman for storing RFID/UUID
identifiers that link Bambu Lab spools to Spoolman entries. Previously,
users had to manually create this field in Spoolman, causing sync
failures for fresh installations.
Added ensure_tag_extra_field() method to SpoolmanClient that:
- Checks if the 'tag' field exists via GET /api/v1/field/spool/tag
- Creates it via POST if missing
The method is called automatically:
- On app startup when auto-connecting to Spoolman
- When user clicks "Connect" in Spoolman settings