Add Telegram notifications

src/static/admin.html

@@ -119,6 +119,7 @@
       <button class="tab-btn admin-only" data-tab="credentials">AVConnect Credentials</button>
       <button class="tab-btn" data-tab="stats">Statistics</button>
       <button class="tab-btn admin-only" data-tab="admins">Admins</button>
+      <button class="tab-btn admin-only" data-tab="telegram">Notifications</button>
     </nav>
 
     <div class="tab-content">
@@ -286,6 +287,42 @@
         </div>
       </div>
 
+      <!-- ── Telegram / Notifications pane ────────────────────────────────── -->
+      <div id="tab-telegram" class="tab-pane">
+        <h3 style="margin-bottom:1rem">Telegram Notifications</h3>
+        <div class="card" style="max-width:480px">
+          <p style="color:var(--text-muted);font-size:.9rem;margin-bottom:1.25rem">
+            Send a message to a Telegram group or chat every time a gate is opened.
+            Create a bot via <a href="https://t.me/BotFather" target="_blank" rel="noopener" style="color:var(--primary)">@BotFather</a>,
+            add it to your group, and paste its token and the chat ID below.
+          </p>
+          <form id="telegram-form">
+            <div class="field">
+              <label for="tg-token">Bot Token</label>
+              <input id="tg-token" type="password" autocomplete="off"
+                     placeholder="Leave empty to keep current" />
+            </div>
+            <div class="field">
+              <label for="tg-chat-id">Chat / Group ID</label>
+              <input id="tg-chat-id" type="text" autocomplete="off"
+                     placeholder="e.g. -1001234567890" required />
+            </div>
+            <div class="field">
+              <label style="display:flex;align-items:center;gap:.75rem;cursor:pointer;margin:0">
+                <input type="checkbox" id="tg-enabled" checked style="width:1.1rem;height:1.1rem;flex-shrink:0;cursor:pointer" />
+                <span style="font-weight:600">Enable notifications</span>
+              </label>
+            </div>
+            <p id="tg-status" style="font-size:.85rem;color:var(--text-muted);margin-bottom:.75rem"></p>
+            <p id="tg-error" class="error-msg hidden"></p>
+            <div style="display:flex;gap:.75rem;flex-wrap:wrap">
+              <button type="submit" class="btn btn-primary">Save</button>
+              <button type="button" id="btn-tg-test" class="btn btn-ghost">Send test message</button>
+            </div>
+          </form>
+        </div>
+      </div>
+
     </div><!-- /.tab-content -->
   </div><!-- /#admin-view -->