MCP platform server scaffolding

[cstns]

Description

Lays the groundwork for the MCP platform tools server. No functional endpoint yet, just the wiring so subsequent PRs have somewhere to land.

• Adds @modelcontextprotocol/sdk and zod as dependencies
• Registers expertPlatformAutomation feature flag, same gate as expertAssistant (AI + expert enabled)
• Reorganizes forge/ee/routes/mcp/: renames existing registration routes to registrations.js, adds empty server.js shell, new index.js router wires both up
• Route shell at POST /api/v1/mcp returns 501 for now, gates on feature flag, rejects non-user tokens
• Existing registration endpoints (/api/v1/teams/:teamId/mcp/*) are unchanged

Related Issue(s)

closes #7426

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 85.52632% with 11 lines in your changes missing coverage. Please review.
✅ Project coverage is 76.97%. Comparing base (9f6c480) to head (1ec0bb6).

Files with missing lines	Patch %	Lines
forge/ee/routes/mcp/registrations.js	83.05%	10 Missing ⚠️
forge/ee/routes/mcp/server.js	92.30%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7596      +/-   ##
==========================================
+ Coverage   76.95%   76.97%   +0.02%     
==========================================
  Files         411      413       +2     
  Lines       21094    21111      +17     
  Branches     5141     5144       +3     
==========================================
+ Hits        16233    16251      +18     
+ Misses       4861     4860       -1     

Flag	Coverage Δ
backend	76.97% <85.52%> (+0.02%)	⬆️

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[n-lark]

looks good to me