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>

games/views/session.py

@@ -254,7 +254,7 @@ def add_session(request: HttpRequest, game_id: int = 0) -> HttpResponse:
         request,
         AddForm(form, request=request, fields=_session_fields(form), submit_class=""),
         title="Add New Session",
-        scripts=mark_safe(ModuleScript("search_select.js")),
+        scripts=mark_safe(ModuleScript("dist/search_select.js")),
     )
 
 
@@ -269,7 +269,7 @@ def edit_session(request: HttpRequest, session_id: int) -> HttpResponse:
         request,
         AddForm(form, request=request, fields=_session_fields(form), submit_class=""),
         title="Edit Session",
-        scripts=mark_safe(ModuleScript("search_select.js")),
+        scripts=mark_safe(ModuleScript("dist/search_select.js")),
     )