perf(P6C.T12): optimistic UI for mute / mentions-only / archive / pin / device-revoke

Audit of write-actions revealed that send (and edit via realtime UPDATE) are
already optimistic via local state insertion in `useConversationMessages`,
and friend nicknames are pure-local localStorage. Five user-write actions
were waiting on the ~100-200 ms server roundtrip + realtime echo:

* Toggle mute (`setConversationMutedUntil`)
* Toggle mentions-only (`setConversationMentionsOnly`)
* Toggle archive (`setConversationArchived`)
* Pin / unpin message (`pinMessage` / `unpinMessage`)
* Revoke device (`revokeDevice` RPC)

All five now flip local state synchronously and roll back on failure. The
existing realtime subscriptions reconcile canonically (no-op when the
optimistic patch already matches the server row), so this is purely a UX
latency improvement — no protocol or persistence changes.

Reactions (`toggleReaction` / `voteExclusive`) were intentionally skipped
this round: rollback semantics for the exclusive-vote path with multiple
sequential awaits are messy enough to warrant a dedicated pass.

apps/desktop/src/hooks/useOwnDevices.ts

@@ -64,10 +64,37 @@ export function useOwnDevices(): {
 
   const revoke = useCallback(
     async (deviceId: string) => {
-      await revokeDevice(supabase, deviceId);
-      await refresh();
+      // Optimistic: flip `revokedAt` on the row so the "Abgemeldet" badge
+      // appears on the same frame as the click. Capture a snapshot so we
+      // can restore exactly on RPC failure (the realtime subscription's
+      // own UPDATE echo would otherwise reconcile back to "not revoked"
+      // anyway). Skip if the row isn't in our list — nothing to undo.
+      let snapshot: DeviceRecord[] | null = null;
+      const stampedAt = new Date().toISOString();
+      setState((prev) => {
+        if (!prev.devices.some((d) => d.id === deviceId)) return prev;
+        snapshot = prev.devices;
+        return {
+          ...prev,
+          devices: prev.devices.map((d) =>
+            d.id === deviceId ? { ...d, revokedAt: d.revokedAt ?? stampedAt } : d,
+          ),
+        };
+      });
+      try {
+        await revokeDevice(supabase, deviceId);
+        // Skip the eager refresh: the realtime UPDATE on `devices` triggers
+        // refresh() via the subscription and the optimistic row already
+        // shows the badge. Avoids a list flicker between optimistic and
+        // canonical state.
+      } catch (err) {
+        if (snapshot) {
+          setState((prev) => ({ ...prev, devices: snapshot! }));
+        }
+        throw err;
+      }
     },
-    [refresh],
+    [],
   );
 
   return { devices: state.devices, loading: state.loading, error: state.error, refresh, revoke };