enhancement: robust MQTT auto-reconnect with exponential backoff

[theKorzh]

Fixes MQTT connection loss without automatic reconnection. Previously, the app made no reconnection attempts after MQTT connection loss. When the connection dropped, the MQTT Proxy would silently stop working, and the app would never attempt to reconnect — requiring users to manually restart the app or reconnect node. This PR implements a infinite reconnection retry loop with exponential backoff.

Why This Implementation Is Necessary

The KMQTT library does NOT have built-in auto-reconnect functionality.

As confirmed by the library owner in issue #51:

"auto-reconnect is something I want to implement but I am not sure when I will be able to do it. In the meantime it's possible to obtain a similar behaviour by creating a new client object every time."

This PR provides the auto-reconnect functionality that the library itself does not yet offer.

Possible fixes: #4016 and related MQTT reconnection issues.

[jamesarich]

This will need to be rebased onto main before I can consider reviewing. I like the idea of it though. 👍

[theKorzh]

Rebased onto latest main. Should be ready for review now.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 91 lines in your changes missing coverage. Please review.
✅ Project coverage is 19.76%. Comparing base (7c9d007) to head (9ddf973).

Files with missing lines	Patch %	Lines
...stic/core/network/repository/MQTTRepositoryImpl.kt	0.00%	91 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4963      +/-   ##
==========================================
- Coverage   19.81%   19.76%   -0.06%     
==========================================
  Files         575      575              
  Lines       18926    18974      +48     
  Branches     2825     2832       +7     
==========================================
  Hits         3750     3750              
- Misses      14615    14663      +48     
  Partials      561      561              

Flag	Coverage Δ
host-unit	19.76% <0.00%> (-0.06%)	⬇️

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Files with missing lines	Coverage Δ
...stic/core/network/repository/MQTTRepositoryImpl.kt	0.00% <0.00%> (ø)