fix: restore frontend source code (src/web/) that was accidentally deleted

Frontend source is needed for development/building the SPA.
Only Node.js runtime server code should be removed.

src/web/pages/settings.route-selector-modal.architecture.test.ts

@@ -0,0 +1,13 @@
+import { describe, expect, it } from 'vitest';
+import { readFileSync } from 'node:fs';
+import { resolve } from 'node:path';
+
+describe('Settings route selector modal extraction', () => {
+  it('no longer keeps a downstream route selector inside Settings', () => {
+    const source = readFileSync(resolve(process.cwd(), 'src/web/pages/Settings.tsx'), 'utf8').replace(/\r\n/g, '\n');
+
+    expect(source).not.toContain("import RouteSelectorModal from './settings/RouteSelectorModal.js'");
+    expect(source).not.toContain('selectorOpen');
+    expect(source).not.toContain('selectorRoutes');
+  });
+});