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/018_chat_histories.sql

@@ -0,0 +1,26 @@
+-- Migration: 018_chat_histories
+-- Adds a dedicated table for saving and retrieving agent chat histories.
+
+CREATE TABLE IF NOT EXISTS chat_histories (
+    id          UUID        PRIMARY KEY DEFAULT gen_random_uuid(),
+    session_id  TEXT        NOT NULL,
+    title       TEXT,
+    channel     TEXT,
+    agent_id    TEXT,
+    project_id  UUID        REFERENCES projects(guid) ON DELETE SET NULL,
+    messages    JSONB       NOT NULL DEFAULT '[]',
+    summary     TEXT,
+    metadata    JSONB       NOT NULL DEFAULT '{}',
+    created_at  TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    updated_at  TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+CREATE INDEX IF NOT EXISTS idx_chat_histories_session_id ON chat_histories(session_id);
+CREATE INDEX IF NOT EXISTS idx_chat_histories_project_id ON chat_histories(project_id) WHERE project_id IS NOT NULL;
+CREATE INDEX IF NOT EXISTS idx_chat_histories_channel    ON chat_histories(channel)    WHERE channel IS NOT NULL;
+CREATE INDEX IF NOT EXISTS idx_chat_histories_agent_id   ON chat_histories(agent_id)   WHERE agent_id IS NOT NULL;
+CREATE INDEX IF NOT EXISTS idx_chat_histories_created_at ON chat_histories(created_at DESC);
+
+CREATE INDEX IF NOT EXISTS idx_chat_histories_fts
+    ON chat_histories
+    USING GIN (to_tsvector('simple', coalesce(title, '') || ' ' || coalesce(summary, '')));