Add interactive release search (M6)

Release listing and grab in the shared arr client, a full-screen release
list (sort, hide rejected, rejection reasons, confirmation before grabbing
rejected releases; Usenet only), and a season/episode picker for Sonarr.
Overlays are now a stack so dialogs can open above the release list.
Add a fake Newznab indexer to the dev setup.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

internal/arr/client.go

@@ -26,7 +26,7 @@ func NewClient(baseURL, apiKey string) *Client {
 	return &Client{
 		baseURL: strings.TrimRight(baseURL, "/"),
 		apiKey:  apiKey,
-		http:    &http.Client{Timeout: 30 * time.Second},
+		http:    &http.Client{Timeout: 2 * time.Minute}, // interactive release searches query every indexer
 	}
 }