Improve status displayed on camera stream

[Gold872]

• Display error message (no stack trace) if exception is thrown
• Display whether or not it's waiting for an image to be sent

Should help with troubleshooting camera streams that won't display

[codecov]

Codecov Report

Attention: Patch coverage is 84.93151% with 11 lines in your changes missing coverage. Please review.

Project coverage is 77.28%. Comparing base (6df4287) to head (407b62a).
Report is 1 commits behind head on main.

✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
lib/widgets/mjpeg.dart	76.19%	10 Missing ⚠️
.../widgets/nt_widgets/multi-topic/camera_stream.dart	96.77%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #201      +/-   ##
==========================================
+ Coverage   76.01%   77.28%   +1.27%     
==========================================
  Files          80       80              
  Lines        8644     8701      +57     
==========================================
+ Hits         6571     6725     +154     
+ Misses       2073     1976      -97     

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