feat(core): FK for user_id columns; MCP search requires user

- Add fk_entries_user_id, fk_entries_history_user_id, fk_audit_log_user_id (ON DELETE SET NULL)
- Add scripts/cleanup-orphan-user-ids.sql for pre-deploy orphan user_id cleanup
- Remove deprecated SERVER_MASTER_KEY / per-user key wrap helpers from secrets-core
- secrets-mcp: require authenticated user for secrets_search; improve body-read failure response
- Bump secrets-mcp to 0.2.1

Made-with: Cursor

crates/secrets-mcp/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "secrets-mcp"
-version = "0.2.0"
+version = "0.2.1"
 edition.workspace = true
 
 [[bin]]