Add calendar time tracking and /app route restructure

[Berget1411]

Summary

• Added a new calendar time-tracking experience, including a calendar page, event sheet, toolbar, active timer card, and supporting utilities/styles.
• Moved app routes under /app and refreshed redirects/navigation to match the new route layout.
• Tightened auth/session and cross-subdomain behavior, plus updated server, deployment, and shared UI packages to support the new flow.
• Brought in TanStack Start best-practice guidance and refreshed UI primitives/theme tokens across the workspace.

Testing

• Not run.
• Suggested check: open the app and verify /app, /app/calendar, and legacy redirects resolve correctly.
• Suggested check: create/edit calendar entries and confirm timer state, overlays, and navigation work in both light and dark modes.
• Suggested check: validate auth flows across subdomains and confirm deploy pipelines complete with the new route structure.