Add web UI, AGPL3, notifications, continue watching, bulk watched, storage stats, scheduler

License:
- GPL3 → AGPL3

New features:
- Web interface (--web [port]): axum/tokio server with SSE progress, library browser,
  download trigger, watched toggle; embedded single-page HTML/JS UI
- Desktop notifications via notify-rust when downloads complete or fail
- Continue Watching sidebar entry showing videos with saved resume positions
- Bulk select mode: select multiple videos, mark all watched/unwatched at once
- Storage stats: channel disk usage shown in sidebar next to video count
- Scheduled channel checks: configurable interval (hours), auto re-downloads all
  tracked channels using channel_url from info.json; enabled in Settings

Theme fixes:
- Scene Queen: remove override_text_color so active button text uses fg_stroke
  (dark navy on neon green) instead of near-white — fixes unreadable contrast
- Trans: override_text_color → hot pink #cc0066 for pink-tinted text throughout

Settings additions:
- Auto-check channels toggle + interval_hours DragValue
- Web UI port setting

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

src/main.rs

@@ -7,8 +7,27 @@ mod downloader;
 mod library;
 mod theme;
 mod tray;
+mod web;
 
 fn main() -> eframe::Result<()> {
+    let args: Vec<String> = std::env::args().collect();
+
+    // --web [port] → run the web interface instead of the GUI
+    if let Some(pos) = args.iter().position(|a| a == "--web") {
+        let mut cfg = {
+            let cwd = std::env::current_dir().unwrap_or_else(|_| std::path::PathBuf::from("."));
+            config::Config::load(&cwd.join("config.toml"))
+                .unwrap_or_else(|_| config::Config::default_with_dir(cwd.join("channels")))
+        };
+        // Override port if provided after --web
+        if let Some(port_str) = args.get(pos + 1) {
+            if let Ok(port) = port_str.parse::<u16>() {
+                cfg.web.port = port;
+            }
+        }
+        web::run(cfg);
+    }
+
     let native_options = eframe::NativeOptions {
         viewport: eframe::egui::ViewportBuilder::default()
             .with_inner_size([1280.0, 820.0])