fix: call_imports

[TEJASNARAYANS]

What Changed?

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Why?

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Checklist

• I have read the CONTRIBUTING.md guide.
• My code follows the project's style guidelines.
• I have added tests that prove my fix is effective or my feature works.
• I have updated documentation where needed.

[greptile-apps]

Greptile Summary

This PR updates the call-import flow and related integrations. The main changes are:

• Requires and maps recording_url schema parameters.
• Adds Exotel API host validation and fallback handling.
• Uses credentialed Exotel downloads for CSV recording URLs.
• Adds GCS Workload Identity signed URL support.
• Updates the call-import UI, docs, and tests.

Confidence Score: 4/5

This is close, but the legacy schema case should be fixed before merging.

• Existing schemas without recording_url can still be selected.
• Those schemas can still create rows without a mapped recording URL.
• The Exotel host and CSV download changes address the reviewed call-import paths.

app/models/schemas.py, app/api/v1/routes/call_imports.py

Important Files Changed

Filename	Overview
app/models/schemas.py	Requires recording_url in schema validation, but existing saved schemas still need migration or selection-time blocking.
app/api/v1/routes/call_imports.py	Treats recording_url as required during mapping and moves the diarisation default route before the UUID route.
app/services/telephony/exotel_client.py	Adds Exotel REST API host parsing, validation, and fallback behavior.
app/workers/tasks/process_call_import_row.py	Uses credentialed Exotel downloads for CSV-supplied recording URLs after call-id lookup does not produce audio.
app/services/storage/gcs_service.py	Adds IAM signBlob support for GCS signed URL generation with ADC and Workload Identity.
frontend/src/pages/callImports/components/MappingPanel.tsx	Improves persisted mapping hydration and updates cached call-import details after saving mappings.

_{Reviews (2): Last reviewed commit: "fix: updating test cases" | Re-trigger Greptile}

[greptile-apps]

Migrate legacy schemas

This validation only runs when a schema create or update payload is submitted. Existing schemas that were saved without a recording_url parameter can still be listed and selected for a new telephony-backed import. In that path, mapping only iterates the parameters that exist, so no recording_url value is created and imported rows can still be stored with recording_url=None. Add a migration/backfill or reject these schemas when selected so legacy schemas cannot produce rows without the CSV recording URL mapping.