refactor(windows): remove unused cloud backend features

[1lck]

Summary

• remove unsupported Lithe account, subscription, enterprise policy, settings sync, collaboration, telemetry, and hosted AI code from Windows
• keep AI provider access local/BYOK and keep GitHub authentication independent of a Lithe account
• separate lithe.top website/static resource configuration from retired backend APIs
• use GitHub Releases directly for Windows updates
• add regression coverage preventing retired cloud service URLs from returning

Closes#281

Validation

• bun run typecheck
• bun run build
• focused Bun tests: 13 passed
• Windows Frontend timing harness: 2 passed, no slow tests
• ./.agents/skills/write-stable-tests/scripts/verify-test-stability.sh
• ./scripts/verify-windows-boundaries.sh
• git diff --check

Known test-suite issue

The full Bun suite reports 444 passed and 3 unrelated failures. The unchanged IME keymap test fails independently, while the two workspace save tests pass when run in isolation, indicating existing suite-order/shared-state pollution.

[1lck]

@lithe review

[github-actions]

Lithe Review

结论： ❓ 审查未完成

审查状态：cancelled。
请查看本次 Actions 日志与诊断附件后重新召唤。