fix(web): stabilize calendar refresh status

[tyler-dane]

Summary

• Prevent the returning-user refresh from retriggering after its own metadata transition.
• Keep established calendars calm during incremental updates; show setup status only for a calendar that has never become healthy.
• Use provider-agnostic, user-focused status copy.

Simplicity

A single mount-lifecycle ref breaks the feedback loop without changing the existing focus-after-hidden refresh. Shared status constants remove duplicated copy.

Automated validation

• Full web suite: 1,548 passing tests.
• Playwright E2E and accessibility suites passed.
• bun run lint and bun type-check passed (lint reports one existing warning in self-host/docker-compose.test.ts).

Independent review

No actionable findings. The reviewer confirmed the gate preserves refresh-on-return and the durable connection state correctly distinguishes setup from routine catch-up.

Test plan

• bun packages/scripts/src/testing/test-parallel.ts web -- packages/web/src/sse/hooks/useSyncFocusRefresh.test.ts packages/web/src/auth/google/hooks/useConnectGoogle/useConnectGoogle.util.test.ts packages/web/src/components/Sidebar/CalendarList/CalendarListHeader.test.tsx
• bun test:web
• bun test:e2e
• bun test:a11y
• bun run lint
• bun type-check