refactor(auth): migrate session storage to JWT with persistent secret (#508)

- Replace in-memory session Map with stateless JWT tokens
- Add jose library for JWT signing and verification
- Implement persistent JWT secret storage in ~/.config/openchamber
- Support OPENCODE_JWT_SECRET environment variable override
- Update SessionAuthGate and useServerSessionStatus hooks
- Remove session cleanup timer (JWTs are stateless)

Co-authored-by: Jovines <jovines@qq.com>

packages/ui/src/hooks/useServerSessionStatus.ts

@@ -78,6 +78,10 @@ export function useServerSessionStatus() {
           headers: { Accept: 'application/json' },
         }).then(async (r) => {
           if (!r.ok) {
+            console.warn('[useServerSessionStatus] API returned', r.status);
+            if (r.status === 401) {
+              console.warn('[useServerSessionStatus] Authentication required - session may have expired');
+            }
             throw new Error(String(r.status));
           }
           return (await r.json()) as ServerSnapshotResponse;