0.35.0: per-stack Update button on the Stacks page

Adds an inline "Update (pull latest images & recreate)" action to each
row of the stacks table, next to start/stop/restart/edit — for both the
local host and remote agents. Wires the existing updateImages action and
the agent "update" lifecycle action through StacksTable's new onUpdate prop.

Also bumps backend/version.py to 0.35.0 so it tracks the frontend version
again (it had drifted to 0.33.0 while package.json moved to 0.34.x).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/pages/Stacks.tsx

@@ -23,7 +23,7 @@ const STATUS_FILTERS: Record<string, StatusFilter> = {
 
 export function Stacks() {
   const isAdmin = useAuthStore((s) => s.user?.role === "admin");
-  const { busyId, start, stop, restart } = useStackActions();
+  const { busyId, start, stop, restart, updateImages } = useStackActions();
   // The dashboard explore bar deep-links here with ?q= / ?filter=.
   const [params] = useSearchParams();
   const [q, setQ] = useState(params.get("q") ?? "");
@@ -137,6 +137,7 @@ export function Stacks() {
           onStart={start}
           onStop={stop}
           onRestart={restart}
+          onUpdate={isAdmin ? updateImages : undefined}
           emptyText={q ? "No stacks match your search." : "No stacks yet. Create one with “New Stack”."}
         />
       </section>