dkg: add nickname flag

[DiogoSantoss]

Add --nickname flag to DKG.
Peers will send their nickname via sync protocol which will be logged upon connecting for the first time:

17:38:03.733 INFO dkg        Connected to peer 1 of 3                 {"peer": "affectionate-kitchen", "nickname": "Alice"}
17:38:03.742 INFO dkg        Connected to peer 2 of 3                 {"peer": "amiable-mirror", "nickname": "Bob"}

category: feature
ticket: #4059

[Copilot]

Pull Request Overview

This PR adds a --nickname flag to the DKG command to allow operators to set human-friendly peer identifiers. When peers connect via the sync protocol, their nicknames are exchanged and logged, improving the operator experience by making peer connections more recognizable.

Key Changes

• Added nickname field to the DKG sync protocol (protobuf message)
• Peers send and display nicknames when connecting during DKG ceremony
• Flag includes validation for a 32-character maximum length

Reviewed Changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
cmd/dkg.go	Adds --nickname CLI flag with 32-character validation
dkg/dkg.go	Passes nickname through to sync protocol initialization
dkg/protocol.go	Forwards nickname parameter to startSyncProtocol
dkg/sync/client.go	Stores nickname as immutable state and includes it in sync messages
dkg/sync/server.go	Extracts nickname from incoming messages and includes it in connection logs
dkg/sync/sync_test.go	Updates tests to initialize nicknames for all test nodes
dkg/dkgpb/v1/sync.proto	Adds nickname field to MsgSync protobuf message
dkg/dkgpb/v1/sync.pb.go	Generated protobuf code for nickname field

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[sonarqubecloud]

Quality Gate passed

Issues
2 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov]

Codecov Report

❌ Patch coverage is 55.00000% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 56.39%. Comparing base (426ba79) to head (f92d3ef).
⚠️ Report is 39 commits behind head on main.

Files with missing lines	Patch %	Lines
cmd/dkg.go	0.00%	5 Missing ⚠️
dkg/dkgpb/v1/sync.pb.go	0.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4105      +/-   ##
==========================================
+ Coverage   56.37%   56.39%   +0.02%     
==========================================
  Files         245      245              
  Lines       31169    31183      +14     
==========================================
+ Hits        17571    17586      +15     
- Misses      11284    11291       +7     
+ Partials     2314     2306       -8     

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[KaloyanTanev]

Good to note that this will make it incompatible with previous versions.
Either way we allow DKG only with the same MAJOR.MINOR, so it's not something new.