Add MCP registration views and update API response structure

[Steve-Mcl]

Description

• Updated the GET MCP registrations to return an object with a count and a servers array, instead of a raw array - this design was a copy of neighbouring table "pipelines"
• Added views MCPRegistrationSummary and MCPRegistrationSummaryList with helper functions and return a sanitized list of mcp server registrations from the GET endpoint

NOTE: In the interest of time (impending release + current task) I have not added tests. If tests are a requirement of this PR, please let me know. I will add a follow issue to retro unit test

Fixed up existing unit test

Related Issue(s)

closes https://github.com/FlowFuse/security/issues/112

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

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 76.30%. Comparing base (36a21d0) to head (1980dd1).
⚠️ Report is 12 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6425      +/-   ##
==========================================
+ Coverage   76.28%   76.30%   +0.01%     
==========================================
  Files         394      395       +1     
  Lines       19806    19819      +13     
  Branches     4746     4746              
==========================================
+ Hits        15109    15122      +13     
  Misses       4697     4697              

Flag	Coverage Δ
backend	76.30% <100.00%> (+0.01%)	⬆️

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