Fix Expert errors when device are present in MCPRegistrations

[cstns]

Description

• Handle device id inconsistency when upserting MCPRegistations table.
• don't query live state for devices when retrieving features

Related Issue(s)

closes #6583

Checklist

• I have read the contribution guidelines
• Suitable unit/system level tests have been added and they pass
• Documentation has been updated
  • Upgrade instructions
  • Configuration details
  • Concepts
• Changes flowforge.yml?
  • Issue/PR raised on FlowFuse/helm to update ConfigMap Template
  • Issue/PR raised on FlowFuse/CloudProject to update values for Staging/Production
• Link to Changelog Entry PR, or note why one is not needed.

Labels

• Includes a DB migration? -> add the area:migration label

[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 76.61%. Comparing base (8e3b5b3) to head (1fb1965).
⚠️ Report is 10 commits behind head on main.

Files with missing lines	Patch %	Lines
forge/ee/routes/mcp/index.js	33.33%	4 Missing ⚠️
forge/routes/api/expert.js	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6584      +/-   ##
==========================================
- Coverage   76.62%   76.61%   -0.02%     
==========================================
  Files         398      398              
  Lines       20093    20100       +7     
  Branches     4836     4839       +3     
==========================================
+ Hits        15397    15400       +3     
- Misses       4696     4700       +4     

Flag	Coverage Δ
backend	76.61% <50.00%> (-0.02%)	⬇️

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