feat: add Claude Enterprise analytics integration

[aimanmuzaffar95]

Summary

Adds a new claude_enterprise datasource plugin for Claude Enterprise Analytics API ingestion.

This PR includes:

• Backend plugin entrypoint, connection/scope/scope-config APIs, test-connection flow, and blueprint v2 pipeline planning
• Tool-layer models and migrations for connections, scopes, summaries, analytics records, usage reports, cost reports, skills, connectors, chat projects, plugins, and artifacts
• Collectors and extractors for Claude Enterprise Analytics endpoints, with raw payload preservation
• Conversion of supported Claude Enterprise user activity records into ai_activities
• Config UI registration for Claude Enterprise, including Analytics API key, organization ID, endpoint, proxy, and rate limit fields
• Grafana dashboards for Claude Enterprise adoption/cost reporting and unified Claude Platform + Enterprise reporting
• README/spec/implementation docs plus synthetic fixtures, unit tests, roundtrip tests, and snapshot-style E2E coverage

Does this close any open issues?

Closes xx

Screenshots

N/A

Other Information

This implementation is based on official Anthropic documentation and synthetic fixtures. Live Claude Enterprise Analytics API smoke validation is deferred and documented in the implementation plan.