S2: On-site berth status visible to boaters

[xishell]

Persona

Visiting boater

User outcome

As a visiting boater, I want to be able to physically see the status of the berth, so that I know if it is available without checking the website.

The dashboard is great from shore, but once you are on the water you need an immediate physical signal. The LED at each berth is that signal.

Acceptance Criteria

• LED shows green when berth is free, red when occupied
• LED state matches the latest mesh-published occupancy within 1 second
• LED is visible in daylight and at night
• LED supports a "reserved" booking-override state distinct from free/occupied