feat: Add email settings management and templates functionality

- Implemented email settings configuration in the admin panel, allowing for SMTP settings and notification preferences.
- Created a new template for email settings with fields for SMTP host, port, username, password, sender address, and recipients.
- Added JavaScript functionality to handle loading, saving, and validating email settings.
- Introduced email templates management, enabling the listing, editing, and saving of email templates.
- Updated navigation to include links to email settings and templates.
- Added tests for email settings and templates to ensure proper functionality and validation.

templates/admin/admin_email_settings.html

@@ -0,0 +1,81 @@
+{% extends "_base.html" %}
+{% block title %}Email Settings{% endblock %}
+{% block heading %}Email Notification Settings{% endblock %}
+{% block extra_styles %}
+<link rel="stylesheet" href="/static/css/admin.css" />
+{% endblock %}
+{% block content %}
+<div class="form-section">
+  <h2>SMTP Configuration</h2>
+  <p>
+    Adjust the SMTP server configuration and notification preferences used for
+    contact form alerts and newsletter messaging. Values saved here override the
+    environment defaults documented in <code>.env</code>.
+  </p>
+
+  <div id="message"></div>
+
+  <form id="emailSettingsForm" class="email-settings-form">
+    <div class="form-row">
+      <div class="form-group">
+        <label for="smtpHost">SMTP Host</label>
+        <input type="text" id="smtpHost" name="smtp_host" autocomplete="off" required />
+      </div>
+      <div class="form-group">
+        <label for="smtpPort">SMTP Port</label>
+        <input type="number" id="smtpPort" name="smtp_port" min="1" max="65535" required />
+      </div>
+    </div>
+
+    <div class="form-row">
+      <div class="form-group">
+        <label for="smtpUsername">SMTP Username</label>
+        <input type="text" id="smtpUsername" name="smtp_username" autocomplete="username" />
+      </div>
+      <div class="form-group">
+        <label for="smtpPassword">SMTP Password</label>
+        <input type="password" id="smtpPassword" name="smtp_password" autocomplete="current-password" />
+      </div>
+    </div>
+
+    <div class="form-row">
+      <div class="form-group">
+        <label for="smtpSender">Sender Address</label>
+        <input type="email" id="smtpSender" name="smtp_sender" autocomplete="email" required />
+      </div>
+      <div class="form-group">
+        <label for="smtpRecipients">Notification Recipients</label>
+        <textarea id="smtpRecipients" name="smtp_recipients" rows="3" placeholder="comma-separated emails"></textarea>
+      </div>
+    </div>
+
+    <div class="form-row">
+      <div class="form-group">
+        <label class="checkbox-inline">
+          <input type="checkbox" id="smtpUseTls" name="smtp_use_tls" />
+          Use TLS when sending mail
+        </label>
+      </div>
+      <div class="form-group">
+        <label class="checkbox-inline">
+          <input type="checkbox" id="notifyContactForm" name="notify_contact_form" />
+          Email notifications for new contact submissions
+        </label>
+      </div>
+      <div class="form-group">
+        <label class="checkbox-inline">
+          <input type="checkbox" id="notifyNewsletter" name="notify_newsletter_signups" />
+          Confirmation emails for newsletter signups
+        </label>
+      </div>
+    </div>
+
+    <div class="form-group" style="margin-top: 20px;">
+      <button type="submit" class="btn btn-primary">Save Email Settings</button>
+    </div>
+  </form>
+</div>
+{% endblock %}
+{% block extra_scripts %}
+<script src="/static/js/admin.js"></script>
+{% endblock %}