feat(admin-settings): show/hide toggle on SMTP password field

Wrap the SMTP password input in a relative container with an
eye / eye-off toggle button so admins can reveal the value while
typing — helps catch copy-paste artifacts and typos when
re-applying credentials after a reset.

State scoped to the field's own x-data block so it doesn't leak
into the parent Alpine context. autocomplete=new-password
prevents browsers from autofilling stale values.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

app/modules/core/templates/core/admin/settings.html

@@ -435,9 +435,22 @@
                                 <label class="block text-sm font-medium text-gray-700 dark:text-gray-300 mb-1">SMTP Username</label>
                                 <input type="text" x-model="emailForm.smtp_user" placeholder="username" class="block w-full px-3 py-2 text-gray-700 dark:text-gray-300 bg-white dark:bg-gray-600 border border-gray-300 dark:border-gray-500 rounded-lg focus:outline-none focus:ring-2 focus:ring-purple-600" />
                             </div>
-                            <div>
+                            <div x-data="{ showSmtpPassword: false }">
                                 <label class="block text-sm font-medium text-gray-700 dark:text-gray-300 mb-1">SMTP Password</label>
-                                <input type="password" x-model="emailForm.smtp_password" placeholder="Enter new password" class="block w-full px-3 py-2 text-gray-700 dark:text-gray-300 bg-white dark:bg-gray-600 border border-gray-300 dark:border-gray-500 rounded-lg focus:outline-none focus:ring-2 focus:ring-purple-600" />
+                                <div class="relative">
+                                    <input :type="showSmtpPassword ? 'text' : 'password'"
+                                           x-model="emailForm.smtp_password"
+                                           placeholder="Enter new password"
+                                           autocomplete="new-password"
+                                           class="block w-full px-3 py-2 pr-10 text-gray-700 dark:text-gray-300 bg-white dark:bg-gray-600 border border-gray-300 dark:border-gray-500 rounded-lg focus:outline-none focus:ring-2 focus:ring-purple-600" />
+                                    <button type="button"
+                                            @click="showSmtpPassword = !showSmtpPassword"
+                                            :aria-label="showSmtpPassword ? 'Hide password' : 'Show password'"
+                                            class="absolute inset-y-0 right-0 flex items-center px-3 text-gray-500 hover:text-gray-700 dark:text-gray-400 dark:hover:text-gray-200 focus:outline-none">
+                                        <span x-show="!showSmtpPassword" x-html="$icon('eye', 'w-4 h-4')"></span>
+                                        <span x-show="showSmtpPassword" x-html="$icon('eye-off', 'w-4 h-4')"></span>
+                                    </button>
+                                </div>
                                 <p class="mt-1 text-xs text-gray-500 dark:text-gray-400">Leave blank to keep existing</p>
                             </div>
                             <div class="flex items-center gap-4">