feat(ai): wire up workspace RAG bulk reindex + manual "Reindex now"

The WORKSPACE_CREATE_EMBEDDINGS / WORKSPACE_DELETE_EMBEDDINGS jobs were
enqueued (on AI Search enable/disable) but had no AI_QUEUE handler, so
existing pages were never indexed ("Indexed 0 of N pages") and disabling
never purged embeddings.

- EmbeddingProcessor: handle WORKSPACE_CREATE_EMBEDDINGS (bulk reindex all
  live pages) and WORKSPACE_DELETE_EMBEDDINGS (purge workspace embeddings)
- EmbeddingIndexerService: add reindexWorkspace() (skips when embeddings
  unconfigured; per-page error isolation) and removeWorkspace()
- PageRepo.getIdsByWorkspace(), PageEmbeddingRepo.deleteByWorkspace()
- AiSettingsService.reindex() + admin-only POST /workspace/ai-settings/reindex
- Frontend: "Reindex now" button, service call and mutation
- Stable per-workspace jobId with remove-before-add so a stale job can't
  block future reindexes; cancel the delayed purge on enable/reindex so it
  can't wipe freshly-built embeddings

apps/client/src/features/workspace/queries/ai-settings-query.ts

@@ -8,6 +8,7 @@ import {
   getAiSettings,
   updateAiSettings,
   testAiConnection,
+  reindexAiEmbeddings,
   IAiSettings,
   IAiSettingsUpdate,
   IAiTestResult,
@@ -52,3 +53,23 @@ export function useTestAiConnectionMutation() {
     mutationFn: () => testAiConnection(),
   });
 }
+
+export function useReindexAiEmbeddingsMutation() {
+  const { t } = useTranslation();
+  const queryClient = useQueryClient();
+
+  return useMutation<IAiSettings, Error, void>({
+    mutationFn: () => reindexAiEmbeddings(),
+    onSuccess: () => {
+      notifications.show({ message: t("Reindexing started") });
+      queryClient.invalidateQueries({ queryKey: aiSettingsKey });
+    },
+    onError: (error) => {
+      const errorMessage = error["response"]?.data?.message;
+      notifications.show({
+        message: errorMessage ?? t("Failed to start reindexing"),
+        color: "red",
+      });
+    },
+  });
+}