feat: schema graph via FK introspection

- GET .../db-connections/:id/foreign-keys — per-dialect
  information_schema/pragma query through dbx_execute_query,
  identifier-whitelisted, read-role gated
- Databases page: Graph tab renders tables as radial SVG nodes with
  FK edges; hover highlights adjacency, click inspects the table
- demo stubs for edges + wider demo table set

Authored By: TDvorak <[email protected]>

packages/api-client/src/generated/models/DBForeignKeyEdge.ts

@@ -0,0 +1,13 @@
+/* generated using openapi-typescript-codegen -- do not edit */
+/* istanbul ignore file */
+/* tslint:disable */
+/* eslint-disable */
+export type DBForeignKeyEdge = {
+    schema?: string;
+    table: string;
+    column: string;
+    ref_schema?: string;
+    ref_table: string;
+    ref_column: string;
+};
+

packages/api-client/src/generated/models/DBForeignKeysResponse.ts

@@ -0,0 +1,11 @@
+/* generated using openapi-typescript-codegen -- do not edit */
+/* istanbul ignore file */
+/* tslint:disable */
+/* eslint-disable */
+import type { DBForeignKeyEdge } from './DBForeignKeyEdge';
+export type DBForeignKeysResponse = {
+    edges: Array<DBForeignKeyEdge>;
+    raw?: string;
+    note?: string;
+};
+