feat(api): optional refresh param on GET /api/graphics-elements

Review SHOULD-FIX (#145): the SPA graphics picker could go stale because
Blazor ran RefreshGraphicsElements (disk->DB sync) before listing, while the
API endpoint never refreshed — a newly added .yml would not appear. GET
/api/graphics-elements?refresh=true now sends RefreshGraphicsElements before
the list query; default false leaves existing callers untouched. The playback
troubleshooting screen passes refresh=true. Controller tests cover
refresh-iff-true ordering; regenerated OpenAPI v1.json (endpoint index and
generated TS schemas unchanged - query params are not part of either).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

ErsatzTV/wwwroot/openapi/v1.json

@@ -4874,7 +4874,17 @@
           "Graphics Elements"
         ],
         "summary": "Get all graphics elements",
+        "description": "Returns all graphics elements. Pass refresh=true to first re-sync the on-disk graphics element definitions into the database (matching the legacy Blazor behavior) so newly added files appear.",
         "operationId": "GetGraphicsElements",
+        "parameters": [
+          {
+            "name": "refresh",
+            "in": "query",
+            "schema": {
+              "type": "boolean"
+            }
+          }
+        ],
         "responses": {
           "200": {
             "description": "OK",