feat(ui): add maintenance page for task management

* Implement maintenance page with task and log display
* Add backfill and metadata retry functionality
* Integrate grid component for project display in thoughts page
* Update types for maintenance tasks and logs
* Enhance sidebar and shell for new maintenance navigation

migrations/_old/010_fulltext_index.sql

@@ -0,0 +1,3 @@
+-- Full-text search index on thought content for semantic fallback when no embeddings exist.
+create index if not exists thoughts_content_fts_idx
+    on thoughts using gin(to_tsvector('simple', content));