feat: consolidate database management work

Add catalog-owned logical relationships and runtime snapshots, extend the database-management UI and validation coverage, and document the updated operational workflow.

Keep active sensitive-generation status in a tooltip and indicator, and update the layout E2E to follow the history action in its new database-scoped location.

frontend/src/api/client.test.ts

@@ -152,6 +152,15 @@ test.each([
   ["sensitive_data_suggestion_history_request_invalid", "Sensitive suggestion history parameters are invalid."],
   ["sensitive_data_suggestion_history_failed", "Sensitive suggestion history could not be loaded."],
   ["sensitive_data_suggestion_run_not_found", "The sensitive suggestion run was not found."],
+  ["relationship_not_found", "The relationship no longer exists. Refresh and try again."],
+  ["relationship_duplicate", "This relationship already exists."],
+  ["relationship_target_not_unique", "The target column must be the only primary-key column of its table."],
+  ["relationship_type_incompatible", "Source and target column types are not compatible."],
+  ["relationship_read_only", "Physical relationships are read-only."],
+  ["relationship_request_invalid", "The relationship request is invalid."],
+  ["relationship_operation_failed", "The relationship operation failed."],
+  ["relationship_schema_stale", "Synchronize the current database schema before managing logical relationships."],
+  ["column_not_found", "The selected catalog column was not found. Refresh and try again."],
 ])("maps the catalog error code %s to safe local copy", async (code, message) => {
   const fetchSpy = vi.spyOn(globalThis, "fetch").mockResolvedValue(
     new Response(JSON.stringify({ code, message: "provider detail must not be trusted" }), {