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>

ts/add_game.ts

@@ -0,0 +1,12 @@
+import { syncSelectInputUntilChanged } from "./utils.js";
+
+const syncData = [
+  {
+    source: "#id_name",
+    source_value: "value",
+    target: "#id_sort_name",
+    target_value: "value",
+  },
+];
+
+syncSelectInputUntilChanged(syncData, "form");