feat: prepare for Angular 20 upgrade

- Update GitHub Actions to use Node.js v22 and actions/setup-node@v4
- Fix Electron debug.ts TypeScript error for devToolsMode union types
- Prepare compatibility for Angular 20 requirements

electron/debug.ts

@@ -77,7 +77,7 @@ export const initDebug = (
   opts: {
     enabled?: boolean | null;
     showDevTools?: boolean;
-    devToolsMode?: string;
+    devToolsMode?: 'bottom' | 'left' | 'right' | 'undocked' | 'detach' | 'previous';
     mode?: string;
   },
   isAddReload: boolean,

src/typings/ical.d.ts

@@ -0,0 +1,37 @@
+// Type override for ical.js to fix TypeScript v5.8+ compatibility issue
+declare module 'ical.js' {
+  namespace ICAL {
+    class Time {
+      static now(): Time;
+      icaltype: string;
+    }
+
+    class VCardTime extends Time {
+      // Override the property to fix TypeScript error TS2610
+      icaltype: string;
+    }
+
+    class Component {
+      constructor(jCal: any);
+      getAllSubcomponents(name?: string): Component[];
+    }
+
+    class Timezone {
+      constructor(options: any);
+      tzid: string;
+    }
+
+    const TimezoneService: {
+      has(tzid: string): boolean;
+      register(timezone: Timezone): void;
+      remove(tzid: string): void;
+    };
+
+    const helpers: {
+      updateTimezones(comp: Component): Component;
+    };
+
+    function parse(icalData: string): any;
+    function stringify(jCal: any): string;
+  }
+}