Add MCP platform tool definitions

[cstns]

Description

Adds the full set of platform tool definitions for the MCP server. 22 tools across 7 domain files, all prefixed with platform. and using the app.inject() pattern to call existing HTTP routes.

• teams.js (2): list-teams, get-team
• applications.js (3): list-applications, get-application, create-application
• instances.js (6): list-instances, get-instance, get-instance-status, get-instance-logs, check-name-availability, create-instance
• snapshots.js (2): list-snapshots, create-snapshot
• devices.js (4): list-devices, get-device, list-device-snapshots, create-device-snapshot
• catalog.js (3): list-instance-types, list-stacks, list-blueprints
• navigation.js (2): open-editor, open-instance

All read tools have readOnlyHint: true annotations. Write tools (create-application, create-instance, create-snapshot, create-device-snapshot) have readOnlyHint: false. No destructive tools in this first pass, those will come later alongside human-in-the-loop confirmation.

Also fixes CORS for the hijacked POST response by setting headers manually on reply.raw before handing off to the MCP transport.
Builds on #7429. Intentionally excludes manage-instance, update-device, and all destructive/delete operations for now.

Related Issue(s)

closes #7430

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 12.14953% with 94 lines in your changes missing coverage. Please review.
✅ Project coverage is 76.70%. Comparing base (1d61cac) to head (c3ebbf5).

Files with missing lines	Patch %	Lines
forge/ee/lib/mcp/tools/instances.js	6.45%	29 Missing ⚠️
forge/ee/lib/mcp/tools/devices.js	10.52%	17 Missing ⚠️
forge/ee/lib/mcp/tools/navigation.js	12.50%	14 Missing ⚠️
forge/ee/lib/mcp/tools/applications.js	14.28%	12 Missing ⚠️
forge/ee/lib/mcp/tools/snapshots.js	15.38%	11 Missing ⚠️
forge/ee/lib/mcp/tools/catalog.js	10.00%	9 Missing ⚠️
forge/ee/routes/mcp/server.js	50.00%	2 Missing ⚠️

Additional details and impacted files

@@                      Coverage Diff                      @@
##           7429_mcp-endpoint-handler    #7599      +/-   ##
=============================================================
- Coverage                      77.03%   76.70%   -0.33%     
=============================================================
  Files                            415      421       +6     
  Lines                          21163    21270     +107     
  Branches                        5148     5160      +12     
=============================================================
+ Hits                           16303    16316      +13     
- Misses                          4860     4954      +94     

Flag	Coverage Δ
backend	76.70% <12.14%> (-0.33%)	⬇️

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