perf: harden quotas and reduce compression overhead

migrations/012_task_query_indexes.sql

@@ -0,0 +1,8 @@
+CREATE INDEX IF NOT EXISTS idx_tasks_user_created_at
+  ON tasks(user_id, created_at DESC);
+
+CREATE INDEX IF NOT EXISTS idx_tasks_user_status_created_at
+  ON tasks(user_id, status, created_at DESC);
+
+CREATE INDEX IF NOT EXISTS idx_tasks_status_created_at
+  ON tasks(status, created_at DESC);