feat: add ledger backup safety workflow

confirm dcy-002 and add REQ/BAT evidence

add ledger backup/status metadata workflow

document restore as runbook/script-only guarded operation

add synthetic DB backup/restore smoke tests

docs/interface-contract.md

@@ -4,7 +4,7 @@
 - Baseline Seed: `.stage-pilot/bootstrap/baseline.yaml`
 - Status: draft
 - Owner: Jarca / project maintainer
-- Last Updated (KST): 2026-06-26 22:24
+- Last Updated (KST): 2026-06-27 10:17
 - Source Discovery / Batch: bootstrap-baseline
 
 ## Project Summary
@@ -21,7 +21,8 @@
 - Stability: internal but should preserve existing success response shapes for compatibility.
 
 ### Representative Tool Groups
-- Health: `ledger_health_check`
+- Health: `ledger_health_check`, `get_ledger_db_status`
+- Operational backup: `create_ledger_backup`, `list_ledger_backups`, `get_ledger_backup_status` (restore is intentionally not exposed as MCP)
 - Accounts: `create_ledger_account`, `list_ledger_accounts`
 - Transactions: `create_ledger_transaction`, `list_ledger_transactions`, `update_ledger_transaction`, `delete_ledger_transaction`
 - Budgets/reports: `create_ledger_budget`, `list_ledger_budgets`, monthly/category/fixed/budget/investable reports
@@ -36,6 +37,7 @@
 
 ### Outputs
 - Python dictionary payloads containing success data, counts, records, previews, reports, or error details.
+- Backup/status tools return metadata-only DB evidence: path, size, mtime, sha256, integrity check, table row counts, and aggregate totals.
 - Existing success shape compatibility is preferred; new fields should be additive where possible.
 
 ### Errors
@@ -46,7 +48,8 @@
 
 ### Compatibility Rules
 - Preserve existing success response shapes unless a migration/REQ explicitly approves a breaking change.
-- Do not write secrets or raw passwords into persistent output, skill files, or committed documentation.
+- Additive backup/status/list/hash tools are allowed; restore execution must not be added as an MCP tool.
+- Do not write secrets, raw passwords, raw_payload, full merchant/counterparty dumps, or full account identifiers into persistent output, skill files, or committed documentation.
 - Source evidence should remain auditable through raw fields and import batch records.
 
 ## Interface: Streamlit Dashboard
@@ -90,6 +93,8 @@
 - All import flows should support preview before mutation where implemented.
 - Dedupe should use deterministic source/external IDs or same-account/date/type/amount/merchant evidence.
 - Import batch metadata should support rollback and audit.
+- Broad mutation workflows should capture metadata-only DB status and backup evidence before/after risky operations.
+- Restore execution is limited to script/runbook workflows and explicit approval, not MCP tools.
 - Financial data and passwords are sensitive runtime inputs and should not be committed.
 
 ## Current Gaps / Planned Changes
@@ -99,3 +104,4 @@
 
 ## Change Log
 - 2026-06-26 22:24 KST: Created by `bootstrap-baseline` from repository observation.
+- 2026-06-27 10:17 KST: BAT-002/REQ-002 기준으로 backup/status/list/hash MCP contract와 restore 비노출 정책 추가.