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/007_embeddings_table.sql

@@ -0,0 +1,16 @@
+create table if not exists embeddings (
+  id        bigserial   primary key,
+  guid      uuid        not null default gen_random_uuid(),
+  thought_id uuid       not null references thoughts(guid) on delete cascade,
+  model     text        not null,
+  dim       int         not null,
+  embedding vector      not null,
+  created_at timestamptz default now(),
+  updated_at timestamptz default now(),
+  constraint embeddings_guid_unique          unique (guid),
+  constraint embeddings_thought_model_unique unique (thought_id, model)
+);
+
+create index if not exists embeddings_thought_id_idx on embeddings (thought_id);
+
+alter table thoughts drop column if exists embedding;