feat: Implement scheduling functionality for playlist synchronization

- Added a new scheduler module using APScheduler to manage scheduled sync jobs.
- Introduced cron expression validation and job scheduling based on user-defined settings.
- Enhanced frontend to support schedule settings, including cron, daily, and weekly modes.
- Updated API service to handle fetching and saving schedule settings.
- Modified StrategySelector component to include schedule management UI.
- Added new types for schedule settings and modes in the frontend.
- Updated requirements to include APScheduler for scheduling capabilities.

frontend/services/api.ts

@@ -1,4 +1,4 @@
-import { Playlist, ServerType, ApiResponse, PlexServerConnection, PlexConnectionSettings, PlexLibrary, RegexReplacement, SyncStrategy } from '../types';
+import { Playlist, ServerType, ApiResponse, PlexServerConnection, PlexConnectionSettings, PlexLibrary, RegexReplacement, SyncStrategy, ScheduleSettings } from '../types';
 
 const API_BASE = import.meta.env.VITE_API_BASE_URL || '';
 
@@ -97,6 +97,20 @@ export const apiService = {
     return handleResponse(response);
   },
 
+  async getScheduleSettings(): Promise<ApiResponse<ScheduleSettings & { nextRun?: string }>> {
+    const response = await fetch(`${API_BASE}/api/schedule`);
+    return handleResponse(response);
+  },
+
+  async saveScheduleSettings(settings: ScheduleSettings): Promise<ApiResponse<null>> {
+    const response = await fetch(`${API_BASE}/api/schedule`, {
+      method: 'PUT',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify(settings),
+    });
+    return handleResponse(response);
+  },
+
   async getPlaylists(serverType: ServerType, signal?: AbortSignal, localPath?: string): Promise<ApiResponse<Playlist[]>> {
     const params = new URLSearchParams({ server: serverType.toLowerCase() });
     if (serverType === ServerType.LOCAL && localPath) {