Fix bug where UIDs, callsigns, and messages containing embedded null
bytes (0x00) are truncated during compression/decompression. The issue
occurs because strlen() stops at the first null byte, but nanopb char
arrays can contain embedded nulls that are valid data.
This causes Android device UIDs like "ANDROID-e7e455b40002429d" to be
truncated to "ANDROID-e7e455b4" (16 chars instead of 24), breaking
direct messages and contact identification.
The fix adds a pb_string_length() helper that scans for the actual
string length by finding the last non-null character, rather than
stopping at the first null.
Added comprehensive unit tests to prevent regressions:
- Normal strings without embedded nulls
- Strings with embedded null bytes
- Empty strings and edge cases
- Android UID pattern testing
- Multiple embedded nulls scenarios
Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
