Convert add_game.js to TypeScript (issue #17)

- Add ts/utils.ts: fully-typed port of utils.js (onSwap, toISOUTCString,
  syncSelectInputUntilChanged, conditionalElementHandler, disableElementsWhen*,
  getValueFromProperty). Uses document.querySelector throughout; fixes
  removeEventListener bug (was passing function reference instead of named
  listener); uses boolean disabled property instead of string "disabled"/""
- Add ts/add_game.ts: TypeScript conversion of add_game.js, imports
  syncSelectInputUntilChanged from ts/utils.ts (resolves to dist/utils.js
  at runtime)
- Update add_game view to serve compiled dist/add_game.js

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

games/views/game.py

@@ -180,7 +180,7 @@ def add_game(request: HttpRequest) -> HttpResponse:
             ),
         ),
         title="Add New Game",
-        scripts=ModuleScript("search_select.js") + ModuleScript("add_game.js"),
+        scripts=ModuleScript("search_select.js") + ModuleScript("dist/add_game.js"),
     )