Add UI-triggered Alpha Canary redeployment

[Yuqing (mydmdm)]

Summary

• add a checked-in, path-independent scripts/start-huabu.sh for tmux-based source redeployment
• expose owner-only Canary status, origin/alpha check, and fixed redeploy actions behind HUABU_CANARY_REDEPLOY_ENABLED=1
• add Settings controls that show running/remote SHAs and require confirmation before redeploying
• persist redacted runner outcomes and document the Alpha/Canary branch and authorization boundaries

Validation

• pnpm typecheck
• pnpm format
• pnpm lint:fix
• pnpm test
• pnpm check:i18n
• node scripts/check-headers.mjs
• pnpm run build
• bash -n scripts/start-huabu.sh
• node --check scripts/canary-redeploy-runner.mjs

Operational boundary

This is an opt-in personal-development convenience. It updates one checkout in place and intentionally does not provide rollback, service preservation, systemd supervision, automatic installation, publication, or stable promotion. No live redeployment was performed while preparing this PR.

Closes #255