fix(graphql): Add deprecated pullBase field to Pull type

[sentry]

This PR addresses an unhandled GraphQLError occurring when external clients query the non-existent pullBase field on the Pull GraphQL type.

The pullBase field has never existed in our schema; the closest historical field was base, which was renamed to comparedTo in October 2021. To prevent these errors and provide backward compatibility for external consumers, this change introduces pullBase as a deprecated field that aliases to comparedTo.

Changes:

• Added pullBase: Commit @deprecated(reason: "Use comparedTo") to apps/codecov-api/graphql_api/types/pull/pull.graphql.
• Modified apps/codecov-api/graphql_api/types/pull/pull.py to use the existing resolve_base resolver for both comparedTo and the new pullBase field.

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Fixes API-F7D

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Note

Low Risk
Read-only GraphQL compatibility shim with no changes to auth, persistence, or comparison behavior beyond exposing an alias field.

Overview
Adds a deprecated pullBase field on the GraphQL Pull type so clients that still request pullBase stop hitting schema errors; it returns the same base commit as comparedTo, with deprecation directing callers to comparedTo.

The Python resolver for comparedTo is also registered for pullBase, so both fields share the existing resolve_base logic (loading the commit via CommitLoader from pull.compared_to).

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[codecov-notifications]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ All tests successful. No failed tests found.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.65%. Comparing base (65af8ae) to head (7f36969).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2458   +/-   ##
=======================================
  Coverage   91.65%   91.65%           
=======================================
  Files        1341     1341           
  Lines       53342    53343    +1     
  Branches     1649     1649           
=======================================
+ Hits        48888    48889    +1     
  Misses       4133     4133           
  Partials      321      321           

Flag	Coverage Δ
apiunit	94.02% <100.00%> (+<0.01%)	⬆️

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