feat(customers): opt-in debug block on the omde lists, printed in the panel console

Sending X-Debug: 1 makes the five wholesale list endpoints return a counts-only
`debug` block next to the rows: the WHERE that actually ran, how many customers
the scope matches before the grid's own filters, how many customers exist per
kind/active/archived/step and how many are an expert's trading account. The
panel sends the header and console-logs the block when localStorage.debug === '1'.

Off by default; DIAG_LOG=false disables it server-side. No names or mobiles.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

apps/admin-panel/src/api/client.ts

@@ -52,6 +52,11 @@ ax.interceptors.request.use(
     if (config.data instanceof FormData) {
       delete config.headers['Content-Type'];
     }
+    // Opt-in troubleshooting: run `localStorage.setItem('debug', '1')` in the
+    // console and reload; list endpoints then answer with a `debug` block.
+    if (localStorage.getItem('debug') === '1') {
+      config.headers['X-Debug'] = '1';
+    }
     return config;
   },
   (error) => Promise.reject(error),
@@ -67,7 +72,16 @@ ax.interceptors.request.use(
  */
 let redirecting = false;
 ax.interceptors.response.use(
-  (response) => response,
+  (response) => {
+    const debug = response.data?.debug;
+    if (debug && localStorage.getItem('debug') === '1') {
+      console.groupCollapsed(`[DEBUG] ${response.config.url}`);
+      console.log(debug);
+      if (Array.isArray(debug.by_kind)) console.table(debug.by_kind);
+      console.groupEnd();
+    }
+    return response;
+  },
   (error) => {
     if (error?.response?.status === 401 && !redirecting) {
       const onLoginPage = window.location.pathname.endsWith('/auth/login');