feat: RAG search frontend + KB selector + RBAC

- wwwroot/rag/search.ui: search form with KB selector + results area
- wwwroot/rag/search_result.dspy: search DSPY returning widget results
- wwwroot/rag/kb_buttons.dspy: dynamic KB selector buttons
- scripts/init_rbac.py: add search paths to LOGINED

scripts/init_rbac.py

@@ -19,6 +19,7 @@ PUBLIC = ['/api/status', '/api/engines', '/api/kb/list', '/', '/index.ui', '/top
           '/rbac/**']
 LOGINED = ['/api/search', '/api/doc/upload', '/api/doc/delete',
            '/api/dir/create', '/api/dir/delete', '/api/dir/list',
+           '/rag/search.ui', '/rag/search_result.dspy', '/rag/kb_buttons.dspy',
            '/rag/documents_list/']