fix: map custom model_name to actual model in /spend/calculate for cost calculation

[HikaruEgashira]

Title

Fix: Map custom model_name to actual model in /spend/calculate

Relevant issues

#10050

Pre-Submission checklist

• I have added at least 1 test in the tests/litellm/ directory.
• I have added a screenshot of my new test passing locally.
• My PR passes all unit tests on (make test-unit).
• My PR's scope is as isolated as possible, it only solves 1 specific problem.

Type

🐛 Bug Fix

Changes

• Fixes a bug where /spend/calculate did not resolve custom model_name to the actual model for cost calculation.
• Now, if a custom model_name is used in completion_response, it is mapped to the real model defined in the config before cost calculation.

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Name	Status	Preview	Comments	Updated (UTC)
litellm	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Apr 16, 2025 10:01am

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