Add SABnzbd client and Downloads view (M4)

SABnzbd client (queue, history, pause/resume, delete, retry) with lenient
number decoding and API-key-safe errors. Downloads view polls while
visible, shows queue and history, and supports pause, delete (with
confirmation) and retry. Add dev/ with pinned Radarr/Sonarr/SABnzbd
containers wired together for manual testing.

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

internal/ui/app.go

@@ -3,12 +3,14 @@ package ui
 
 import (
 	"fmt"
+	"time"
 
 	"github.com/gdamore/tcell/v2"
 	"github.com/rivo/tview"
 
 	"git.stinnesbeck.com/nils/arr-tui/internal/config"
 	"git.stinnesbeck.com/nils/arr-tui/internal/radarr"
+	"git.stinnesbeck.com/nils/arr-tui/internal/sabnzbd"
 	"git.stinnesbeck.com/nils/arr-tui/internal/sonarr"
 )
 
@@ -18,6 +20,8 @@ type view struct {
 	key  rune
 	name string
 	body tview.Primitive
+	// Optional hooks, called when the view becomes visible / hidden.
+	onShow, onHide func()
 }
 
 // App is the top-level arr-tui application.
@@ -43,11 +47,15 @@ func New(cfg *config.Config) *App {
 		status: tview.NewTextView().SetDynamicColors(true),
 	}
 
+	downloads := newDownloadsView(a, sabnzbd.NewClient(cfg.SABnzbd.URL, cfg.SABnzbd.APIKey),
+		time.Duration(cfg.UI.RefreshSeconds)*time.Second)
+	radarrClient := radarr.NewClient(cfg.Radarr.URL, cfg.Radarr.APIKey)
+	sonarrClient := sonarr.NewClient(cfg.Sonarr.URL, cfg.Sonarr.APIKey)
 	a.views = []view{
-		{'1', "Movies", newSearchView(a, radarrBackend{radarr.NewClient(cfg.Radarr.URL, cfg.Radarr.APIKey)}, cfg.Radarr).root},
-		{'2', "Series", newSearchView(a, sonarrBackend{sonarr.NewClient(cfg.Sonarr.URL, cfg.Sonarr.APIKey)}, cfg.Sonarr).root},
-		{'3', "Downloads", placeholder("Downloads (M4/M5)")},
-		{'4', "Library", placeholder("Library (v0.2)")},
+		{key: '1', name: "Movies", body: newSearchView(a, radarrBackend{radarrClient}, cfg.Radarr).root},
+		{key: '2', name: "Series", body: newSearchView(a, sonarrBackend{sonarrClient}, cfg.Sonarr).root},
+		{key: '3', name: "Downloads", body: downloads.root, onShow: downloads.activate, onHide: downloads.deactivate},
+		{key: '4', name: "Library", body: placeholder("Library (v0.2)")},
 	}
 	for i, v := range a.views {
 		a.pages.AddPage(v.name, v.body, true, i == 0)
@@ -115,6 +123,20 @@ func (a *App) closeModal() {
 	}
 }
 
+// confirm asks a yes/no question; yes runs only if the user picks Delete/Yes.
+func (a *App) confirm(text string, yes func()) {
+	m := tview.NewModal().
+		SetText(text).
+		AddButtons([]string{"Cancel", "Confirm"}). // Cancel first so a stray Enter is safe
+		SetDoneFunc(func(i int, _ string) {
+			a.closeModal()
+			if i == 1 {
+				yes()
+			}
+		})
+	a.openModal(m, 60, 9)
+}
+
 // typing reports whether keystrokes belong to a text field or dialog and must
 // not trigger global shortcuts.
 func (a *App) typing() bool {
@@ -178,6 +200,12 @@ func (a *App) viewShortcut(ev *tcell.EventKey) int {
 }
 
 func (a *App) switchTo(i int) {
+	if hide := a.views[a.active].onHide; hide != nil && i != a.active {
+		hide()
+	}
+	if show := a.views[i].onShow; show != nil && i != a.active {
+		show()
+	}
 	a.active = i
 	a.pages.SwitchToPage(a.views[i].name)
 	a.renderTabs()