Serial monitor redesign: Test box button, InfluxDB row in the checklist

- Test box: restart + start-up capture + online InfluxDB check (data newer
  than the restart), with a status strip; checklist and findings are the
  main view, live log / guided troubleshooting / box details are tabs,
  rarely used actions in a More menu
- light palette on all systems (macOS dark mode made the colours unreadable)
- new rule influx.invalid_value: -inf from a silent microphone makes
  InfluxDB reject every upload (HTTP 400); guide end names it
- exclusive serial port on macOS/Linux: two tool windows no longer split
  the log between them
- InfluxDB check: `since` filter, neutral wording when nothing new arrives

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

kota_tech/diag/engine.py

@@ -73,7 +73,7 @@ MILESTONES = [
     ("wifi_connected", "Connected to Wi-Fi", False),
     ("time_synced", "Clock set from the Internet", False),
     ("clock_verified", "Clock keeps time (RTC verified)", True),
-    ("data_uploaded", "Data uploaded to InfluxDB", False),
+    ("data_uploaded", "Upload accepted by InfluxDB (box log)", False),
     ("ota_registered", "Registered for firmware updates", False),
     ("ota_checked", "Checked for firmware updates", False),
     ("ota_update_started", "Firmware update started", True),