feat: add React Query hooks for admin infrastructure endpoints

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/src/api/queries/admin/database.ts

@@ -0,0 +1,71 @@
+import { useMutation, useQuery, useQueryClient } from '@tanstack/react-query';
+import { adminFetch } from './admin-api';
+
+export interface DatabaseStatus {
+  connected: boolean;
+  version: string;
+  host: string;
+  schema: string;
+}
+
+export interface PoolStats {
+  activeConnections: number;
+  idleConnections: number;
+  pendingConnections: number;
+  maxConnections: number;
+  maxWaitMillis: number;
+}
+
+export interface TableInfo {
+  tableName: string;
+  rowEstimate: number;
+  dataSize: string;
+  indexSize: string;
+}
+
+export interface ActiveQuery {
+  pid: number;
+  durationMs: number;
+  state: string;
+  query: string;
+}
+
+export function useDatabaseStatus() {
+  return useQuery({
+    queryKey: ['admin', 'database', 'status'],
+    queryFn: () => adminFetch<DatabaseStatus>('/database/status'),
+  });
+}
+
+export function useDatabasePool() {
+  return useQuery({
+    queryKey: ['admin', 'database', 'pool'],
+    queryFn: () => adminFetch<PoolStats>('/database/pool'),
+    refetchInterval: 15000,
+  });
+}
+
+export function useDatabaseTables() {
+  return useQuery({
+    queryKey: ['admin', 'database', 'tables'],
+    queryFn: () => adminFetch<TableInfo[]>('/database/tables'),
+  });
+}
+
+export function useDatabaseQueries() {
+  return useQuery({
+    queryKey: ['admin', 'database', 'queries'],
+    queryFn: () => adminFetch<ActiveQuery[]>('/database/queries'),
+    refetchInterval: 15000,
+  });
+}
+
+export function useKillQuery() {
+  const qc = useQueryClient();
+  return useMutation({
+    mutationFn: async (pid: number) => {
+      await adminFetch<void>(`/database/queries/${pid}`, { method: 'DELETE' });
+    },
+    onSuccess: () => qc.invalidateQueries({ queryKey: ['admin', 'database', 'queries'] }),
+  });
+}