Add playlist support to downloader API and frontend

Enhanced the downloader backend and frontend to support playlist URLs for video info and downloads. The API now returns structured playlist information, allows selecting specific videos for download, and returns a ZIP file for playlist downloads. Updated OpenAPI types, removed deprecated parameters (start_time, end_time, playlist_items), and improved Content Security Policy handling in nginx. Refactored frontend to handle playlist selection and updated generated API models accordingly.

frontend/src/api/generated/private/models/videoInfo.ts

@@ -0,0 +1,26 @@
+/**
+ * Generated by orval v7.17.0 🍺
+ * Do not edit manually.
+ * OpenAPI spec version: 0.0.0
+ */
+
+export interface VideoInfo {
+  /** Video ID */
+  id: string;
+  /** Video title */
+  title: string;
+  /**
+   * Video duration in seconds (null if unavailable)
+   * @nullable
+   */
+  duration: number | null;
+  /**
+   * Base64 encoded thumbnail image as data URL (e.g., data:image/jpeg;base64,...)
+   * @nullable
+   */
+  thumbnail: string | null;
+  /** List of available video quality options (e.g., '1080p', '720p', '480p') */
+  video_resolutions: string[];
+  /** List of available audio format options */
+  audio_resolutions: string[];
+}