[subpathdev]

Why

A page that loads doesn't prove the broker works, and old values look like fresh ones. Jan's idea.

What

A dot with a text label in the top right, using what the page already fetches, so there's no backend or contract change:

State	Dot	Label
Server, broker and all thermostats fine	Green	All OK
API can't be reached	Red	No server
connected is false	Red	No broker
A command isn't confirmed (commandFailed)	Red	Office: not confirming
lastSeen is null	Red	Office: no report yet
lastSeen is older than 2 hours	Red	Office: no report since 13:50

The page already refreshes every 5 s, so the dot does too, rather than the 30 s that was suggested.

How to validate

Ran locally against the real broker read-only: both rooms show "All OK" within seconds. Every red state was checked in a browser at phone width with stubbed responses, and it goes back to green afterwards.

Limits

• A dead TRV only turns the dot red after 2 hours, the same threshold as the room's note. TRVs report at least about every 25 minutes, so this could be shorter.
• Green says a thermostat reported, not that the radiator is heating. A dead room sensor doesn't count, since the page falls back to the TRV's temperature.

Risk

Page only. Merging releases a new minor version, but nothing deploys until the chart bump in smart-home.

Rollback

Revert the PR.

🤖 Generated with Claude Code