feat: download dirs, file transfer resume, Wails desktop app, PWA, CI

Daemon:
- Per-network download directories (-download-dir flag, set_download_dir IPC)
- File transfer resume after disconnection: .tmp.meta sidecars survive
  interruption; resume_offset in file-accept lets sender seek and continue
- set_download_dir IPC command; download_dir reported in state_snapshot

Protocol:
- PeerMessage.ResumeOffset (EXT-006) for file transfer resume
- IpcMessage.ShareNetworks json tag changed from "networks" to "network_ids"
  to fix duplicate json tag collision with Networks []NetworkInfo

Desktop app (cmd/app):
- Wails v2 shell embedding daemon logic directly (no subprocess)
- System tray on Linux/Windows via getlantern/systray; macOS hides to Dock
- OS notifications for message_received and file_complete via Wails events
- notray build tag for headless/CI builds without GTK tray headers
- build-app.sh: builds web frontend, copies dist, runs wails build

Web / PWA:
- manifest.json + Apple touch icon meta tags for mobile "Add to Home Screen"
- PNG icons (192px, 512px, 180px) generated from SVG
- Wails EventsOn("notify") hook in App.tsx for native OS notifications

CI:
- .gitea/workflows/build.yml: server binaries cross-compiled for 5 platforms,
  desktop app for Linux amd64, release artifacts published on v* tags

Docs:
- README: download dir, file transfer resume, desktop app, PWA, CI sections
- EXTENSIONS.md: EXT-004 daemon mode marked shipped; EXT-006 resume added
- FUTURE.md: roadmap updated

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

cmd/app/app.go

@@ -0,0 +1,130 @@
+package main
+
+import (
+	"context"
+	"log"
+	"os"
+	"path/filepath"
+
+	"github.com/wailsapp/wails/v2/pkg/runtime"
+
+	"github.com/waste-go/internal/crypto"
+	"github.com/waste-go/internal/ipc"
+	"github.com/waste-go/internal/netmgr"
+	"github.com/waste-go/internal/proto"
+)
+
+const wsPort = 17338
+
+// App is the Wails application backend.
+// It embeds the daemon directly — no subprocess needed.
+// The React frontend connects to the daemon's WebSocket IPC at ws://127.0.0.1:17338,
+// exactly as it does in browser-daemon mode.
+type App struct {
+	ctx context.Context
+	mgr *netmgr.Manager
+}
+
+func newApp() *App {
+	return &App{}
+}
+
+// startup is called when the Wails window is ready. It initialises the daemon,
+// starts the WebSocket IPC listener, sets up the system tray, and begins
+// forwarding message/file events to the webview as OS notifications.
+func (a *App) startup(ctx context.Context) {
+	a.ctx = ctx
+
+	dir := dataDir()
+	id, err := crypto.LoadOrCreate(dir, "")
+	if err != nil {
+		log.Printf("app: identity: %v", err)
+		runtime.MessageDialog(ctx, runtime.MessageDialogOptions{
+			Type:    runtime.ErrorDialog,
+			Title:   "waste — startup error",
+			Message: "Failed to load identity: " + err.Error(),
+		})
+		return
+	}
+	log.Printf("app: peer id: %s  alias: %s", id.PeerID().Short(), id.Alias)
+
+	a.mgr = netmgr.New(netmgr.Config{
+		MasterIdentity: id,
+		StoreDir:       dir,
+	})
+
+	// Forward daemon events to the webview and generate OS notifications.
+	go a.watchEvents()
+
+	// Start the WebSocket IPC server; the webview connects here (daemon mode).
+	go func() {
+		if err := ipc.RunWS(a.mgr, wsPort); err != nil {
+			log.Printf("app: IPC: %v", err)
+		}
+	}()
+
+	log.Printf("app: WebSocket IPC listening on 127.0.0.1:%d", wsPort)
+
+	// System tray (Linux/Windows; no-op on macOS — see tray_darwin.go).
+	a.startTray()
+}
+
+// shutdown is called when the Wails app exits.
+func (a *App) shutdown(ctx context.Context) {
+	if a.mgr != nil {
+		a.mgr.LeaveAll()
+	}
+}
+
+// watchEvents subscribes to all daemon events and emits OS notifications for
+// incoming messages and completed file transfers. The "notify" event is received
+// by the frontend via Wails EventsOn and displayed using the browser Notification API.
+func (a *App) watchEvents() {
+	if a.mgr == nil {
+		return
+	}
+	events := a.mgr.Subscribe()
+	defer a.mgr.Unsubscribe(events)
+
+	for evt := range events {
+		switch evt.Type {
+		case proto.EvtMessageReceived:
+			if evt.Message == nil {
+				continue
+			}
+			// Don't notify for messages sent by the local peer.
+			if a.mgr.MasterIdentity() != nil && evt.Message.From == a.mgr.MasterIdentity().PeerID() {
+				continue
+			}
+			runtime.EventsEmit(a.ctx, "notify", map[string]string{
+				"title": "waste — new message",
+				"body":  evt.Message.Text,
+			})
+
+		case proto.EvtFileComplete:
+			runtime.EventsEmit(a.ctx, "notify", map[string]string{
+				"title": "waste — file received",
+				"body":  filepath.Base(evt.Path),
+			})
+		}
+	}
+}
+
+// dataDir returns the OS-appropriate config directory for identity and stores.
+// macOS: ~/Library/Application Support/waste
+// Linux: ~/.config/waste
+// Windows: %APPDATA%\waste
+func dataDir() string {
+	base, err := os.UserConfigDir()
+	if err != nil {
+		if home, err := os.UserHomeDir(); err == nil {
+			return filepath.Join(home, ".waste")
+		}
+		return ".waste"
+	}
+	dir := filepath.Join(base, "waste")
+	if err := os.MkdirAll(dir, 0o700); err != nil {
+		log.Printf("app: mkdir %s: %v", dir, err)
+	}
+	return dir
+}