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/sonarr/sonarr_test.go

@@ -115,3 +115,36 @@ func TestSearchSeries(t *testing.T) {
 		t.Errorf("body = %v", got)
 	}
 }
+
+func TestEpisodesAndReleaseQueries(t *testing.T) {
+	var queries []string
+	c := newTestClient(t, func(w http.ResponseWriter, r *http.Request) {
+		queries = append(queries, r.URL.Path+"?"+r.URL.RawQuery)
+		if r.URL.Path == "/api/v3/episode" {
+			w.Write([]byte(`[{"id":10,"seriesId":3,"seasonNumber":1,"episodeNumber":2,"title":"Two","hasFile":true}]`))
+			return
+		}
+		w.Write([]byte(`[]`))
+	})
+	ctx := context.Background()
+	eps, err := c.Episodes(ctx, 3)
+	if err != nil || len(eps) != 1 || eps[0].ID != 10 || !eps[0].HasFile || eps[0].EpisodeNumber != 2 {
+		t.Fatalf("episodes = %+v, %v", eps, err)
+	}
+	if _, err := c.EpisodeReleases(ctx, 10); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := c.SeasonReleases(ctx, 3, 1); err != nil {
+		t.Fatal(err)
+	}
+	want := []string{
+		"/api/v3/episode?seriesId=3",
+		"/api/v3/release?episodeId=10",
+		"/api/v3/release?seasonNumber=1&seriesId=3",
+	}
+	for i := range want {
+		if queries[i] != want[i] {
+			t.Errorf("query %d = %q, want %q", i, queries[i], want[i])
+		}
+	}
+}