feat: feed UI, in-app player, offline mode, settings

Adds an end-to-end integration test that runs the real pipeline against
live YouTube Atom feeds, verifying the merged feed is newest-first
across channels.

src/types.ts

@@ -0,0 +1,77 @@
+// Mirrors of the Rust structs in src-tauri/src/models.rs. Field names match
+// serde's output exactly so no mapping layer is needed.
+
+export type DownloadState =
+  | "queued"
+  | "running"
+  | "done"
+  | "failed"
+  | "cancelled";
+
+export interface ChannelWithCount {
+  id: string;
+  title: string;
+  url: string;
+  video_count: number;
+  downloaded_count: number;
+}
+
+export interface FeedItem {
+  id: string;
+  channel_id: string;
+  channel_title: string;
+  title: string;
+  description: string;
+  /** Unix seconds. */
+  published: number;
+  thumb_url: string;
+  thumb_path: string | null;
+  views: number;
+  is_short: boolean;
+  state: DownloadState | null;
+  path: string | null;
+  pct: number | null;
+  error: string | null;
+}
+
+export interface FeedFilter {
+  channel_id?: string | null;
+  search?: string | null;
+  downloaded_only: boolean;
+  hide_shorts: boolean;
+  limit?: number | null;
+}
+
+export interface Prereqs {
+  yt_dlp: string | null;
+  ffmpeg: string | null;
+  library_path: string;
+}
+
+export interface RefreshSummary {
+  channels: number;
+  new_videos: number;
+  failures: string[];
+}
+
+export interface RefreshProgress {
+  done: number;
+  total: number;
+  channel: string;
+}
+
+export interface DownloadProgressEvent {
+  video_id: string;
+  pct: number | null;
+  bytes_done: number;
+  bytes_total: number | null;
+  speed: number | null;
+  eta: number | null;
+}
+
+export interface DownloadStateEvent {
+  video_id: string;
+  state: DownloadState;
+  error: string | null;
+  path: string | null;
+}