feat: add status change timestamps to bookings export

[rlho]

Summary of Changes

Adds per-status timestamp columns to the admin CSV export (/api/bookings/export) so auditors can see each status transition, not just the single "End Event Status".

New columns (in NY timezone, format M/d/yyyy h:mm a):

• Requested At
• First Approved At
• Final Approved At
• Declined At
• Checked In At
• Checked Out At
• No Show At
• Canceled At
• Closed At

This unblocks downstream audit work — e.g. a Late Cancellation tally computed from Canceled At - Booking Start in the existing App Script. Values are read directly from the per-status fields already present on {tenant}-bookings documents; no new collection joins.

Also hardens the date conversion path: switches to the shared toFirebaseTimestamp helper from components/src/client/utils/serverDate.ts and adds a small safeFormat wrapper. Bookings with malformed/legacy timestamp values now render an empty cell instead of crashing the entire export with RangeError: Invalid time value. This fix also covers the pre-existing Booking Start/End Date/Time columns.

Schema Changes

• No tenant schema changes
• Schema changed (describe below)

Checklist

• I linked relevant issue(s) in the Development section
• I checked for existing implementations and confirmed there is no duplication
• I thoroughly tested this feature locally
• I added or updated unit tests (or explained why not in the PR description)
• I attached screenshots or a video demonstrating the feature (or explained why not in the PR description)
• I incorporated Copilot's feedback (or explained why not in the PR description), and marked conversations as resolved
• I confirmed my PR passed all unit and end-to-end (E2E) tests
• I confirmed there are no conflicts
• I requested a code review from at least one other teammate

No unit tests added: the route has no existing test scaffold and the change is mostly column wiring + delegation to an already-tested helper.

Screenshots / Video

CSV output verified locally against the MC dev dataset: new columns populate for bookings with transitions and stay empty for un-traversed statuses; bookings that previously triggered a 500 due to legacy timestamp shapes now export cleanly with empty cells in the affected columns.

[Copilot]

Pull request overview

Adds per-status transition timestamp columns (Requested At, First/Final Approved At, Declined At, Checked In/Out At, No Show At, Canceled At, Closed At) to the admin CSV export, and hardens timestamp parsing by delegating to the shared toFirebaseTimestamp helper with a safeFormat wrapper that returns "" for unparseable values.

Changes:

• Switch local toDate to use toFirebaseTimestamp and return null on bad/missing inputs.
• Add safeFormat and reuse it for both existing Booking Start/End columns and the new status timestamp columns.
• Guard calculateTimeInUse against null toDate results.