feat: Implement email sending utilities and templates for job notifications

- Added email_service.py for sending emails with SMTP configuration.
- Introduced email_templates.py to render job alert email subjects and bodies.
- Enhanced scraper.py to extract contact information from job listings.
- Updated settings.js to handle negative keyword input validation.
- Created email.html and email_templates.html for managing email subscriptions and templates in the admin interface.
- Modified base.html to include links for email alerts and templates.
- Expanded user settings.html to allow management of negative keywords.
- Updated utils.py to include functions for retrieving negative keywords and email settings.
- Enhanced job filtering logic to exclude jobs containing negative keywords.

web/templates/admin/email.html

@@ -0,0 +1,62 @@
+{% extends 'base.html' %} {% block content %}
+<h2>Email Subscriptions</h2>
+<section>
+  <h3>Add Subscription</h3>
+  <form method="post">
+    <input type="hidden" name="csrf_token" value="{{ csrf_token() }}" />
+    <input type="hidden" name="action" value="subscribe" />
+    <label for="email">Email address</label>
+    <input
+      type="email"
+      id="email"
+      name="email"
+      placeholder="alerts@example.com"
+      required
+    />
+    <button type="submit">Subscribe</button>
+  </form>
+</section>
+<section>
+  <h3>Current Recipients</h3>
+  {% if not subscriptions %}
+  <p>No subscriptions yet. Add one above to start sending alerts.</p>
+    <p>You can customize alert content from the <a href="{{ url_for('admin_email_templates') }}">Email Templates</a> page.</p>
+  {% else %}
+  <p>{{ total_active }} active of {{ total }} total.</p>
+  <table>
+    <thead>
+      <tr>
+        <th>Email</th>
+        <th>Status</th>
+        <th>Created</th>
+        <th>Updated</th>
+        <th>Action</th>
+      </tr>
+    </thead>
+    <tbody>
+      {% for sub in subscriptions %}
+      <tr>
+        <td>{{ sub.email }}</td>
+        <td>{{ 'Active' if sub.is_active else 'Inactive' }}</td>
+        <td>{{ sub.created_at }}</td>
+        <td>{{ sub.updated_at }}</td>
+        <td>
+          <form method="post" style="display: inline-flex; gap: 0.5rem">
+            <input type="hidden" name="csrf_token" value="{{ csrf_token() }}" />
+            <input type="hidden" name="email" value="{{ sub.email }}" />
+            {% if sub.is_active %}
+            <input type="hidden" name="action" value="unsubscribe" />
+            <button type="submit">Deactivate</button>
+            {% else %}
+            <input type="hidden" name="action" value="reactivate" />
+            <button type="submit">Reactivate</button>
+            {% endif %}
+          </form>
+        </td>
+      </tr>
+      {% endfor %}
+    </tbody>
+  </table>
+  {% endif %}
+</section>
+{% endblock %}