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 94.11765% with 2 lines in your changes missing coverage. Please review.

Project coverage is 77.13%. Comparing base (bf6f698) to head (81b0fb9).

✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
lib/widgets/mjpeg.dart	94.11%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #201      +/-   ##
==========================================
+ Coverage   75.91%   77.13%   +1.22%     
==========================================
  Files          79       79              
  Lines        8626     8650      +24     
==========================================
+ Hits         6548     6672     +124     
+ Misses       2078     1978     -100     

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