fix: protect token rotation and account runtime state

[LeaningLearner]

Summary

• Serialize account read-modify-write operations while retaining per-account refresh locking.
• Reconcile active auth.json credentials, stop unsafe refresh rotation while Codex is running, and mark stable refresh failures for re-authentication.
• Add in-place OAuth re-authentication with identity checks while preserving local account settings.
• Keep Codex running state global and restore switch/re-auth confirmation flows.
• Allow a confirmed account switch while Codex is running: force-close blocking processes, re-check the process state, switch credentials through the protected backend path, then automatically reopen the Codex desktop app.
• Report the partial-success case clearly when the account switch succeeds but Codex cannot be reopened.
• Add an English/Chinese UI language switch with shared locale-aware date and time formatting.
• Clean up account menu and sort labels by removing duplicate plus signs and leading percent markers.
• Add compatibility handling and regression tests for legacy account data, concurrent refreshes, re-authentication, runtime state, date formatting, and the switch/reopen sequence.

Validation

• pnpm test:frontend — 8 tests passed.
• pnpm build — TypeScript and Vite production build passed.
• cargo test --manifest-path src-tauri/Cargo.toml — 43 tests passed.
• git diff --check — passed.

The local-only packaging override remains excluded from this PR. No credentials or machine-specific account data are included.