Localization stages 2-3: drafts, publishing, translation editor

- games.main_version_id, version visibility (draft/published) and kind
  (original/translation/mod), version_history; migration 0002
- permissions translations.edit and versions.publish
- "Translate" creates a translation draft; publishing merges the changed
  languages into the main version in place (players keep their saves), the
  previous manifest goes to the history and can be restored
- translation API: overview with per-state stats, entries with filters,
  search and scene context, save, glossary, locale font, PO/CSV export/import
- translation editor page: languages and progress, lines and strings,
  filters, autosave, approve/outdated/fuzzy actions, glossary highlighting,
  "play from here" with the scene restored
- player: ?lang= and ?at= from the editor, per-locale font

(models.py and permissions.py for this landed earlier in 9ee3e1f)

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

backend/app/worker.py

@@ -87,6 +87,8 @@ async def convert(version_id: int, source: Path, filename: str) -> bool:
                                                           read_bytes(result.cover_source))
             except OSError:
                 pass
+        if game and game.main_version_id is None:
+            game.main_version_id = version.id
         if game and result.title and game.title == source.name:
             game.title = result.title
         await db.commit()