Add per-feed visibility settings panel

Visitors can hide individual feeds via a gear-icon panel in the header.
Preferences live in localStorage; the server ships the full source list
(name + channel) as window.PETE_SOURCES so the panel lists every feed,
grouped by channel, regardless of what's on the current page.

main.go

@@ -200,7 +200,7 @@ func main() {
 
 	// Start the read-only web UI alongside the Matrix bot.
 	if cfg.Web.Enabled {
-		ws, err := web.New(cfg.Web)
+		ws, err := web.New(cfg.Web, cfg.Sources)
 		if err != nil {
 			slog.Error("web server init failed", "err", err)
 		} else {
@@ -246,7 +246,7 @@ func runLocal(cfg *config.Config) {
 	poller.Start(ctx)
 	slog.Info("local: pollers started")
 
-	ws, err := web.New(cfg.Web)
+	ws, err := web.New(cfg.Web, cfg.Sources)
 	if err != nil {
 		slog.Error("local: web server init failed", "err", err)
 		os.Exit(1)