Dashboard: Telegram-Verknüpfung Button + Modal

- Session-Card-Menü: 'Telegram verknüpfen' zwischen Chat öffnen und Bearbeiten
- Button nur sichtbar wenn Telegram Bot konfiguriert (GET /api/telegram/status)
- Klick generiert 6-stelligen Link-Code (POST /api/telegram/link)
- Modal zeigt '/link CODE' mit Copy-Button, 5 Min gültig
- Neuer Backend-Endpoint GET /api/telegram/status (IsConfigured)
- API-Funktionen: apiTelegramStatus(), apiTelegramLink()
- Modal-CSS nach bestehendem .fe-overlay Pattern

wwwroot/css/dashboard.css

@@ -301,3 +301,77 @@
   background: rgb(from var(--text) r g b / .15);
   color: var(--text);
 }
+
+/* Telegram Link Modal */
+
+.modal-overlay {
+  position: fixed;
+  inset: 0;
+  background: rgb(from var(--f1-bg) r g b / var(--semi-transparent));
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  z-index: 1000;
+}
+
+.telegram-link-modal {
+  background: var(--f2-bg);
+  border: var(--border-width) solid var(--f2-border);
+  border-radius: var(--border-radius);
+  width: 90vw;
+  max-width: 28em;
+  display: flex;
+  flex-direction: column;
+  overflow: hidden;
+}
+
+.telegram-link-modal .modal-header {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  padding: var(--box-padding);
+  border-bottom: var(--border-width) solid var(--f1-border);
+  background: var(--f1-bg);
+}
+
+.telegram-link-modal .modal-header h3 {
+  margin: 0;
+  display: flex;
+  align-items: center;
+  gap: var(--badge-spacing);
+}
+
+.telegram-link-modal .modal-body {
+  padding: var(--box-padding);
+  display: flex;
+  flex-direction: column;
+  gap: var(--box-spacing);
+}
+
+.telegram-code-display {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  gap: var(--box-spacing);
+  padding: var(--box-padding);
+  background: var(--f1-bg);
+  border: var(--border-width) solid var(--f1-border);
+  border-radius: var(--border-radius);
+}
+
+.telegram-code-display code {
+  font-size: calc(var(--font-size) * 1.5);
+  font-weight: bold;
+  letter-spacing: .1em;
+  color: var(--primary);
+  user-select: all;
+}
+
+.telegram-code-hint {
+  opacity: var(--semi-transparent);
+  text-align: center;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  gap: var(--badge-spacing);
+}