refactor: move game-specific import logic into profiles; unblock Tomie import

- Add app/games: GameProfile base, registry, ReaderHooks and renpy/naninovel/
  tomie profiles. pipeline, preflight, detect and mods dispatch via the registry
- Move tomie_* converter modules to app/games/tomie and split out reader hooks,
  import, mod validation and known defects
- Tolerate the 31 authoring defects of the pinned Tomie build as report
  warnings (exact list, per-script counts); any new defect still blocks import
- Frontend: runtime registry (runtimes.ts) with lazy Tomie launcher
- Add profile/registry tests and docs/GAME_PROFILES.md; update IMPORT.md

Full media export of the original Tomie build is not yet verified.

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

backend/app/games/__init__.py

@@ -0,0 +1,8 @@
+"""Game profiles. Add a module here and register it to support a new engine or game build."""
+from app.games.naninovel import NaninovelProfile
+from app.games.registry import register
+from app.games.renpy import RenPyProfile
+from app.games.tomie import TomieProfile
+
+for _profile in (RenPyProfile(), NaninovelProfile(), TomieProfile()):
+    register(_profile)