feat(mcp-server): add action tools (getActionForm, executeAction)

[Scra3]

Summary

Add MCP tools for working with Forest Admin actions:

getActionForm

• Load form fields for an action with dynamic form support
• Shows field types, options, validation, and widget metadata
• Supports multi-page forms
• Returns hints (canExecute, requiredFieldsMissing)

executeAction

• Execute actions with form values
• Support for file download responses (returns base64-encoded data)
• Activity logging with 'executeAction' action

Other changes

• getActionEndpoints helper in schema-fetcher
• ActionEndpointsMap export in agent-caller
• queryWithFileSupport method in agent-client HttpRequester
• executeWithFileSupport method in agent-client Action

Dependencies

This PR is based on #1389 (feat/update) and should be merged after it.

Test plan

• [x] Unit tests for getActionForm tool (25 tests)
• [x] Unit tests for executeAction tool (25 tests)
• [x] All agent-client tests pass (152 tests)
• [x] All mcp-server tests pass (414 tests)

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