feat(auth): harden login flows and finalize quality-check coverage

tests/Architecture/AuthLoginFrontendCleanupContractTest.php

@@ -0,0 +1,34 @@
+<?php
+
+namespace MintyPHP\Tests\Architecture;
+
+use PHPUnit\Framework\TestCase;
+
+class AuthLoginFrontendCleanupContractTest extends TestCase
+{
+    use ProjectFileAssertionSupport;
+
+    public function testLoginCssDoesNotContainLegacyBackToLoginSelector(): void
+    {
+        $content = $this->readProjectFile('web/css/pages/app-login.css');
+
+        $this->assertStringNotContainsString('.back_to_login', $content);
+    }
+
+    public function testLoginPasswordToggleUsesDuplicateBindingGuard(): void
+    {
+        $content = $this->readProjectFile('web/js/components/app-password-toggle.js');
+
+        $this->assertStringContainsString("input.dataset.passwordToggleBound === '1'", $content);
+        $this->assertStringContainsString("input.dataset.passwordToggleBound = '1';", $content);
+        $this->assertStringContainsString("toggle.dataset.passwordToggleBound = '1';", $content);
+    }
+
+    public function testLoginPasswordHintsUsesDuplicateBindingGuard(): void
+    {
+        $content = $this->readProjectFile('web/js/components/app-password-hints.js');
+
+        $this->assertStringContainsString("container.dataset.passwordHintsBound === '1'", $content);
+        $this->assertStringContainsString("container.dataset.passwordHintsBound = '1';", $content);
+    }
+}