feat: harden auth flows and server mobile navigation

Add normalized email identity rate limiting for registration and forgot-password requests, and refresh Sentinel status from restart broadcasts.

Rework server sidebars and navbar for mobile menus and active status visibility.

tests/Unit/EmailIdentityHelperTest.php

@@ -0,0 +1,16 @@
+<?php
+
+it('normalizes plus and dotted email identity variants', function () {
+    expect(normalize_email_identity('Ke.VinMcFadden+one@BTInternet.com'))->toBe('kevinmcfadden@btinternet.com');
+    expect(normalize_email_identity('k.e.v.i.n.m.c.f.a.d.d.e.n+two@btinternet.com'))->toBe('kevinmcfadden@btinternet.com');
+});
+
+it('returns null for blank or malformed email identities', function (?string $email) {
+    expect(normalize_email_identity($email))->toBeNull();
+})->with([
+    null,
+    '',
+    'not-an-email',
+    '@example.com',
+    'local@',
+]);