feat(tags): show a character's fandom on its chip (truncated)

A character chip with a fandom only rendered a bare arrow. Surface the fandom
NAME inline, truncated to 15 chars (full name in the tooltip). Resolve the name
via a Tag self-join in both tag paths the modal uses — list_for_image
(/api/images/<id>/tags) and gallery get_image_with_tags
(/api/gallery/image/<id>) — so chips show the fandom on first open and after any
reload. Falls back to the bare arrow when only fandom_id is known. Operator-asked
2026-06-09.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

backend/app/api/tags.py

@@ -172,6 +172,7 @@ async def list_tags_for_image(image_id: int):
                 "name": t.name,
                 "kind": t.kind.value,
                 "fandom_id": t.fandom_id,
+                "fandom_name": t.fandom_name,
             }
             for t in tags
         ]