fix(types): Fix type narrowing in BaseQuerySet.update_with_returning

[JoshFerge]

Summary

Add isinstance check for col before accessing query.annotations.get() and add explicit type annotation for new_order_by list to handle mixed types (str, Combinable, Expression).

Changes

• Add isinstance(col, str) check before dictionary access
• Add explicit list[Any] type annotation for new_order_by
• Handle both string and Combinable types in order_by processing

Test plan

• Existing tests pass
• Mypy type checking passes

[codecov]

Codecov Report

❌ Patch coverage is 12.50000% with 7 lines in your changes missing coverage. Please review.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/sentry/db/models/manager/base_query_set.py	12.50%	7 Missing ⚠️

❌ Your patch check has failed because the patch coverage (12.50%) is below the target coverage (50.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@             Coverage Diff             @@
##           master   #103016      +/-   ##
===========================================
- Coverage   80.75%    80.64%   -0.12%     
===========================================
  Files        9145      9140       -5     
  Lines      395020    392796    -2224     
  Branches    24968     24968              
===========================================
- Hits       319002    316768    -2234     
- Misses      75617     75627      +10     
  Partials      401       401