feat: add birthday calendar feature with settings and localization

components/calendar/calendar-sidebar-panel.tsx

@@ -2,13 +2,14 @@
 
 import { useState, useRef, useEffect, useMemo } from "react";
 import { useTranslations } from "next-intl";
-import { Globe, ListTodo, Pencil, RefreshCw, Share2, Trash2 } from "lucide-react";
+import { Globe, ListTodo, Pencil, RefreshCw, Share2, Trash2, Cake } from "lucide-react";
 import { cn, formatDateTime } from "@/lib/utils";
 import type { Calendar } from "@/lib/jmap/types";
 import { CalendarColorPicker } from "@/components/settings/calendar-management-settings";
 import { useCalendarStore } from "@/stores/calendar-store";
 import { useSettingsStore } from "@/stores/settings-store";
 import { useTaskStore } from "@/stores/task-store";
+import { BIRTHDAY_CALENDAR_ID } from "@/lib/birthday-calendar";
 import { toast } from "@/stores/toast-store";
 import type { IJMAPClient } from '@/lib/jmap/client-interface';
 
@@ -164,6 +165,9 @@ export function CalendarSidebarPanel({
               )}
             </>
           )}
+          {cal.id === BIRTHDAY_CALENDAR_ID && (
+            <Cake className="w-3 h-3 text-muted-foreground flex-shrink-0" />
+          )}
         </button>
 
         {/* Subscription context menu on right-click */}

components/settings/calendar-settings.tsx

@@ -19,6 +19,7 @@ export function CalendarSettings() {
     showWeekNumbers,
     enableCalendarTasks,
     showTasksOnCalendar,
+    showBirthdayCalendar,
     calendarHoverPreview,
     updateSetting,
   } = useSettingsStore();
@@ -98,6 +99,16 @@ export function CalendarSettings() {
         />
       </SettingItem>
 
+      <SettingItem
+        label={t('show_birthday_calendar')}
+        description={t('show_birthday_calendar_desc')}
+      >
+        <ToggleSwitch
+          checked={showBirthdayCalendar}
+          onChange={(checked) => updateSetting('showBirthdayCalendar', checked)}
+        />
+      </SettingItem>
+
       {isFeatureEnabled('calendarTasksEnabled') && (
       <>
       <SettingItem