feat: complete i18n for settings, add language flags, reduce Synology calendar noise

- Added 70+ translation keys across all 5 languages (EN/DE/FR/ES/IT)
- Replaced 45+ hardcoded strings in settings with translated versions
- Added flag emojis to language dropdown (🇬🇧🇩🇪🇫🇷🇪🇸🇮🇹)
- Fixed language dropdown jumping back to English (functional updater, correct fallback)
- Downgraded Synology calendar 405/404 errors to warnings for stale calendars

v1.24.0

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "my-weekly-todo-list",
-  "version": "1.23.1",
+  "version": "1.24.0",
   "description": "A web-based weekly task management application that organizes to-dos and calendar events in a single, intuitive weekly view",
   "main": "index.js",
   "scripts": {

src/lib/synology-calendar.ts

@@ -232,7 +232,14 @@ export const getUpcomingEvents = async (
 
     return parsedEvents;
   } catch (error: any) {
+    const msg = error?.message || '';
+    const status = error?.response?.status || error?.status;
+    // Silently handle expected failures (stale/deleted calendars, permission issues)
+    if (status === 405 || status === 404 || msg.includes('405') || msg.includes('Not Allowed') || msg.includes('not found')) {
+      console.warn(`[SYNOLOGY CALENDAR] Calendar unavailable (${status || msg.slice(0, 60)}): ${calendarUrl}`);
+    } else {
       console.error(`[SYNOLOGY CALENDAR] Error fetching events for ${calendarUrl}:`, error);
+    }
     return [];
   }
 };