fix(web): add missing i18n keys for session.inactive banner

[swear01]

The inactive-session banner rendered by SessionChat.tsx referenced two translation keys — session.inactive.autoResume and session.inactive.cannotResume — that were never added to the locale dictionaries, so the UI showed the raw key string.

Added both keys to en.ts and zh-CN.ts.

• EN: This session is inactive. Send a message to resume. / This session is inactive and cannot be resumed.
• ZH: 此会话已停止。发送消息即可恢复。 / 此会话已停止，无法恢复。

Verified with bun typecheck and bun run test (all packages green).

[github-actions]

Findings
No findings.

Summary
Review mode: initial
No issues found in the locale-only diff. Residual risk: no automated check currently guarantees every t(...) key exists in each locale dictionary, so similar missing-key regressions can still slip through elsewhere.

Testing
Not run (automation)

HAPI Bot