feat: implement metadata catalog database management

frontend/src/api/client.ts

@@ -14,6 +14,10 @@ const safeErrorCodes = new Set([
   "git_unavailable", "git_auth_failed", "git_non_fast_forward", "connector_unavailable",
   "semantic_index_incompatible", "pi_management_forbidden", "pi_management_unavailable",
   "pi_management_invalid_config", "pi_management_write_failed",
+  "catalog_unavailable", "database_conflict", "database_invalid", "database_not_found",
+  "database_stale", "database_operation_failed",
+  "schema_sync_conflict", "schema_introspection_failed", "schema_request_invalid",
+  "schema_operation_failed", "sync_run_not_found", "table_stale", "column_stale",
 ]);
 
 type SafeErrorPayload = {
@@ -46,6 +50,19 @@ const localCodeMessages: Record<string, string> = {
   pi_management_unavailable: "Pi management is unavailable.",
   pi_management_invalid_config: "The Pi configuration is invalid.",
   pi_management_write_failed: "The Pi configuration could not be saved.",
+  catalog_unavailable: "The database catalog is unavailable.",
+  database_conflict: "This workspace already has a database configuration.",
+  database_invalid: "The database configuration is invalid.",
+  database_not_found: "The database configuration was not found.",
+  database_stale: "The database configuration changed. Reload and try again.",
+  database_operation_failed: "The database operation failed.",
+  schema_sync_conflict: "A schema synchronization is already active or no longer current.",
+  schema_introspection_failed: "The database schema could not be read safely.",
+  schema_request_invalid: "The schema request is invalid.",
+  schema_operation_failed: "The schema operation failed.",
+  sync_run_not_found: "The synchronization run was not found.",
+  table_stale: "Table metadata changed. Reload and try again.",
+  column_stale: "Column metadata changed. Reload and try again.",
 };
 
 const localStatusMessages: Record<number, string> = {