feat(example): Add packet log and UI improvements

[jamesarich]

This commit enhances the mesh_service_example application by adding a packet log and improving the user interface.

Features:

• A new collapsible "Packet Log" section has been added to the main screen to display timestamped events like connections, disconnections, sent/received packets, and API requests.
• The "Mesh Nodes" list is now a collapsible section to improve layout and user experience.

UI & UX:

• A custom ExampleTheme is introduced, supporting dynamic colors on Android S+ for a more modern look and feel.
• The LazyColumn in MainScreen is now used more effectively by replacing forEach loops with items, which is better for performance.

Bug Fixes & Refinements:

• Fixes the decodeOrNull extension to correctly handle empty ByteString or ByteArray by returning a default/empty proto message instead of null, as Wire decodes empty bytes into an empty message.
• The BroadcastReceiver is now registered as RECEIVER_EXPORTED on Android 13+ to ensure it can receive broadcasts from the Meshtastic service app.

[codecov]

Codecov Report

❌ Patch coverage is 4.87805% with 39 lines in your changes missing coverage. Please review.
✅ Project coverage is 8.54%. Comparing base (854eff6) to head (0b3f62c).
⚠️ Report is 5 commits behind head on main.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...android/meshserviceexample/MeshServiceViewModel.kt	0.00%	32 Missing ⚠️
...htastic/android/meshserviceexample/MainActivity.kt	0.00%	6 Missing ⚠️
...eshtastic/android/meshserviceexample/MainScreen.kt	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##            main   #4455      +/-   ##
========================================
- Coverage   8.57%   8.54%   -0.03%     
========================================
  Files        420     420              
  Lines      14184   14217      +33     
  Branches    2358    2359       +1     
========================================
- Hits        1216    1215       -1     
- Misses     12748   12782      +34     
  Partials     220     220              

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