feat(store): per-account folder_mapping + excluded_folders columns

migrations/0003_account_folder_mapping.down.sql

@@ -0,0 +1,2 @@
+ALTER TABLE accounts DROP COLUMN excluded_folders;
+ALTER TABLE accounts DROP COLUMN folder_mapping;

migrations/0003_account_folder_mapping.up.sql

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+ALTER TABLE accounts ADD COLUMN folder_mapping   JSONB NOT NULL DEFAULT '{}';
+ALTER TABLE accounts ADD COLUMN excluded_folders JSONB NOT NULL DEFAULT '[]';
+
+-- Carry the existing task-wide mapping onto its accounts so behavior is preserved.
+UPDATE accounts a SET folder_mapping = t.folder_mapping
+  FROM tasks t WHERE a.task_id = t.id AND t.folder_mapping <> '{}'::jsonb;