feat(P3.T5): useOwnDevices hook with realtime refresh

Adds useOwnDevices React hook that fetches the user device list via
listOwnDevices and re-fetches on any postgres_changes event on the
devices table, matching the channel/filter convention in AuthContext.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/desktop/src/hooks/useOwnDevices.ts

@@ -0,0 +1,74 @@
+import { useCallback, useEffect, useState } from 'react';
+
+import { type DeviceRecord, listOwnDevices, revokeDevice } from '@chat-app/shared/auth';
+
+import { useAuth } from '../context/AuthContext';
+import { supabase } from '../lib/supabase';
+
+interface State {
+  devices: DeviceRecord[];
+  loading: boolean;
+  error: string | null;
+}
+
+export function useOwnDevices(): {
+  devices: DeviceRecord[];
+  loading: boolean;
+  error: string | null;
+  refresh: () => Promise<void>;
+  revoke: (deviceId: string) => Promise<void>;
+} {
+  const { session } = useAuth();
+  const userId = session?.user.id ?? null;
+  const [state, setState] = useState<State>({ devices: [], loading: true, error: null });
+
+  const refresh = useCallback(async () => {
+    try {
+      setState((s) => ({ ...s, loading: true, error: null }));
+      const list = await listOwnDevices(supabase);
+      setState({ devices: list, loading: false, error: null });
+    } catch (err) {
+      setState((s) => ({
+        ...s,
+        loading: false,
+        error: err instanceof Error ? err.message : 'failed to load devices',
+      }));
+    }
+  }, []);
+
+  useEffect(() => {
+    if (!userId) {
+      setState({ devices: [], loading: false, error: null });
+      return;
+    }
+    void refresh();
+    const channel = supabase
+      .channel('devices:list:' + userId)
+      .on(
+        'postgres_changes',
+        {
+          event: '*',
+          schema: 'public',
+          table: 'devices',
+          filter: 'user_id=eq.' + userId,
+        },
+        () => {
+          void refresh();
+        },
+      )
+      .subscribe();
+    return () => {
+      void supabase.removeChannel(channel);
+    };
+  }, [userId, refresh]);
+
+  const revoke = useCallback(
+    async (deviceId: string) => {
+      await revokeDevice(supabase, deviceId);
+      await refresh();
+    },
+    [refresh],
+  );
+
+  return { devices: state.devices, loading: state.loading, error: state.error, refresh, revoke };
+}