Support check-in time ranges for hotel bookings

[michidk]

Many hotels have a check-in window rather than a single time — e.g. check-in from 15:00 until 22:00. Late arrivals outside that window often require prior arrangement or incur fees.

Currently, the check_in field on day_accommodations stores a single time value. This doesn't capture the cutoff.

Proposal

Support a check-in time range so users (and MCP clients) can record both the earliest and latest check-in times. A few options:

1. Add a check_in_end column to day_accommodations alongside the existing check_in — simple and explicit
2. Store structured text like "15:00-22:00" in the existing check_in field — no schema change but requires parsing
3. Use metadata/JSON to hold the range — flexible but less queryable

Option 1 seems cleanest. The UI could then show "Check-in: 15:00 – 22:00" and warn if an arrival time falls outside the window.

This would be useful both in the planner UI and for MCP clients recommending hotel bookings.

Related: #363

[mauriceboe]

Implemented in dev — will be included in the next release. PR: #672