feat(knowledge): add retry endpoint and 20-char text name limit

Add POST /api/tenant/knowledge/items/retry/:id to re-queue failed parse
tasks, plus a 20-rune cap on text item names with matching frontend
validation. Wires the retry button into the knowledge table with a
colored status tag for clearer state feedback.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/admin-web/src/lib/api.ts

@@ -703,6 +703,9 @@ export const knowledgeApi = {
   removeItem(id: number) {
     return apiClient.remove<null>(`/api/tenant/knowledge/items/${id}`);
   },
+  retryItem(id: number) {
+    return apiClient.post<KnowledgeItem, null>(`/api/tenant/knowledge/items/retry/${id}`, null);
+  },
 };
 
 export const imagesApi = {