fix: wait for backend ready in global-setup, add login retry in milestone test

Root cause: milestone test was the first to run after global-setup completed
the wizard configuration. The backend needed time to detect the config file
and run database migrations, but tests started immediately. This caused
/auth/token requests to fail with net::ERR_FAILED.

Changes:
- global-setup.ts: after wizard setup, poll backend /docs until it returns 200
- milestone.spec.ts: add retry loop (max 3 attempts) for login as extra safety
  and assert token presence before proceeding

global-setup.ts

@@ -74,6 +74,28 @@ async function setupWizard() {
     } else {
       console.log('⚠️ Wizard already configured or on main page');
     }
+
+    // Wait for backend to be ready (it starts after config file is written)
+    const backendURL = process.env.BACKEND_URL || 'http://backend:8000';
+    console.log('⏳ Waiting for backend to be ready...');
+    const maxRetries = 30;
+    for (let i = 0; i < maxRetries; i++) {
+      try {
+        const resp = await page.request.get(`${backendURL}/docs`, { timeout: 3000 });
+        if (resp.ok()) {
+          console.log('✅ Backend is ready!');
+          break;
+        }
+      } catch {
+        // backend not ready yet
+      }
+      if (i === maxRetries - 1) {
+        console.warn('⚠️ Backend did not respond after retries, proceeding anyway...');
+      } else {
+        console.log(`  Waiting for backend... (${i + 1}/${maxRetries})`);
+        await new Promise(r => setTimeout(r, 2000));
+      }
+    }
     
     await browser.close();
     return;