fix: add catch-all API mock and socket.io block for base screenshots

Base screenshots showed loading spinners or were missing entirely because:
1. Unmocked API calls (e.g. /api/people, /api/search/explore) hit the static
   preview server which returns HTML instead of JSON, preventing networkidle
2. Socket.io WebSocket connections never complete handshake, blocking networkidle

Add a catch-all /api/** mock (registered first, so specific mocks take priority)
that returns empty JSON for any unmocked endpoint. Block socket.io connections.
Also add a networkidle timeout fallback in run-scenarios.ts so screenshots are
still captured even if networkidle doesn't resolve within 15s.

https://claude.ai/code/session_01XSTqDJXuR4jaLN7SGm3uES

e2e/src/screenshots/run-scenarios.ts

@@ -97,8 +97,15 @@ for (const scenario of allScenarios) {
       });
     }
 
-    // Navigate to the page
+    // Navigate to the page. Use networkidle so SvelteKit hydrates and API
-    await page.goto(scenario.url, { waitUntil: 'networkidle' });
+    // calls complete, but fall back to domcontentloaded if it times out
+    // (e.g. a persistent connection the catch-all mock didn't cover).
+    try {
+      await page.goto(scenario.url, { waitUntil: 'networkidle', timeout: 15_000 });
+    } catch {
+      console.warn(`networkidle timed out for ${scenario.name}, falling back to current state`);
+      // Page has already navigated, just continue with what we have
+    }
 
     // Wait for specific selector if specified
     if (scenario.waitForSelector) {

e2e/src/ui/mock-network/base-network.ts

@@ -10,6 +10,27 @@ export const setupBaseMockApiRoutes = async (context: BrowserContext, adminUserI
       path: '/',
     },
   ]);
+
+  // Block socket.io connections — these are persistent WebSocket connections
+  // that prevent networkidle from resolving since there's no real server.
+  await context.route('**/api/socket.io**', async (route) => {
+    return route.abort('connectionrefused');
+  });
+
+  // Catch-all for any /api/ endpoint not explicitly mocked below.
+  // Registered FIRST so specific routes (registered after) take priority
+  // (Playwright checks routes in reverse registration order).
+  // Without this, unmocked API calls hit the static preview server which
+  // either hangs or returns HTML, preventing networkidle and causing timeouts.
+  await context.route('**/api/**', async (route) => {
+    const method = route.request().method();
+    return route.fulfill({
+      status: 200,
+      contentType: 'application/json',
+      json: method === 'GET' ? [] : {},
+    });
+  });
+
   await context.route('**/api/users/me', async (route) => {
     return route.fulfill({
       status: 200,