feat: responsive pause/stop, non-blocking update with progress bar, delete saved sessions (1.5.0)

- carve: check cancellation inside chunks and per hit; reassembly stage is cancellable
- status exposes `stopping`; UI shows "Pausing…" immediately
- Tauri update commands run off the UI thread; download percentage reported
- delete autosaved sessions manually (one/all) and by retention setting
- chore(release): 1.5.0

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

apps/gui/ui/index.html

@@ -24,7 +24,7 @@
         <button class="side-action" id="openImageBtn"><svg viewBox="0 0 24 24" width="18" height="18"><path d="M4 7a2 2 0 0 1 2-2h4l2 2h6a2 2 0 0 1 2 2v8a2 2 0 0 1-2 2H6a2 2 0 0 1-2-2z" stroke="currentColor" stroke-width="1.8" fill="none"/></svg>Abrir arquivo de imagem…</button>
         <div class="side-title">Sessões</div>
         <ul id="sessionList" class="list"></ul>
-        <div class="side-title">Recentes <small style="font-weight:400;text-transform:none;letter-spacing:0">(salvas sozinhas)</small></div>
+        <div class="side-title">Recentes <small style="font-weight:400;text-transform:none;letter-spacing:0">(salvas sozinhas)</small> <button class="icon-btn small" id="clearRecentBtn" title="Apagar todas as sessões salvas sozinhas" aria-label="Apagar todas as sessões salvas sozinhas"><svg viewBox="0 0 24 24" width="16" height="16"><path d="M5 7h14M10 7V5h4v2m-6 0l1 12h6l1-12" stroke="currentColor" stroke-width="2" fill="none" stroke-linecap="round" stroke-linejoin="round"/></svg></button></div>
         <ul id="recentList" class="list"></ul>
         <button class="side-action" id="loadSessionBtn"><svg viewBox="0 0 24 24" width="18" height="18"><path d="M12 4v11m0 0l-4-4m4 4l4-4M5 20h14" stroke="currentColor" stroke-width="1.8" fill="none" stroke-linecap="round" stroke-linejoin="round"/></svg>Abrir sessão salva…</button>
       </nav>