Convert search_select.js to TypeScript (issue #17)

- Add ts/search_select.ts: typed port of the SearchSelect/FilterSelect widget.
  Exports SearchSelectOption / SearchSelectChangeDetail as the single source of
  truth for the "search-select:change" event contract
- add_purchase.ts now imports those types via `import type` (no runtime
  coupling), instead of redefining them locally
- Declare window.readSearchSelect in ts/globals.d.ts
- Point the SearchSelect component Media and every view/e2e/test reference at
  the compiled dist/search_select.js
- Update doc comments in common/components/search_select.py to name the TS source

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

tests/test_rendered_pages.py

@@ -64,7 +64,7 @@ class RenderedPagesTest(TestCase):
         components declare their JS and Page() collects it."""
         html = self.get("games:list_games").content.decode()
         self.assertIn("js/filter_bar.js", html)
-        self.assertIn("js/search_select.js", html)
+        self.assertIn("js/dist/search_select.js", html)
         self.assertIn("js/range_slider.js", html)
 
     def test_stats_page_auto_loads_datepicker(self):