NodeWave v0.8.1

Fixes found on the test phones: the map download crash, a radio that would not start, the diagnostics page, the unread badge.

Fixed

• The app restarted at the end of a map download on Android 10 and 11 (Mi Note 10, Honor View 10): the signature check used InputStream.readNBytes, which exists only from Android 13, and the resulting NoSuchMethodError killed the process right after the last byte arrived. It now reads the header with a plain read. A download whose .part is already complete (the finish was cut short) is recognised when the server answers 416 and is kept instead of being fetched again; a .part that does not fit the file is still discarded.
• The radio did not start on a phone whose BLE advertiser slots were all taken (the Honor answered ADVERTISE_FAILED_TOO_MANY_ADVERTISERS, error 9): the whole start was abandoned. It now retries three times and then runs without advertising (it still scans and can connect to the nodes it hears), and the watchdog keeps trying to advertise every 15 seconds.
• The unread badge on the Chats tab sat off the icon and its text was cut; it is now anchored to the icon's corner with the text centred.
• Diagnostics page: the whole page scrolls, texts and buttons stay on one line on every phone width, and the console is much taller.

Changed

• 203 unit tests (new: a complete .part is kept on a 416, an invalid one is discarded).

Debug-signed build for testing: it updates over the other NodeWave pre-releases. Not independently audited, see docs/SECURITY.md.