[Junior-HJ]

⚠️ base-red inherited: #17219

Summary

Port model mapping and custom notes support at provider connection level from sub2api:

• Add notes (free-form text) and model_map (JSON mapping requested model -> actual model) to provider_connections.
• Implement model resolution in request dispatch pipeline and provider execution fallback/cooldown flows.
• Implement dual model accounting (requested_model vs actual_model) across usage_history and call_logs, ensuring usage/pricing calculations run on actual_model.
• Add UI controls to EditConnectionModal to edit notes and modelMap (key-value / JSON input).

Migrations

• 215_connection_notes_model_map.sql
• 216_usage_actual_model.sql

Validation

• npm run check:migration-numbering passing.
• npm run typecheck:core passing.
• Unit tests passing:
  • tests/unit/db/connection-notes-model-map.test.ts
  • tests/unit/db/usage-actual-model.test.ts
  • tests/unit/services/connection-model-map.test.ts
  • tests/unit/providers/connection-model-map-input.test.ts
  • tests/unit/dashboard/edit-connection-modal-notes-model-map.test.tsx