Revert "feat(usage): add api_kind field to microdollar_usage_metadata"

[chrarnoldus]

Reverts #1126

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Files Reviewed (9 files)

• packages/db/src/migrations/0051_chemical_ultimatum.sql
• packages/db/src/migrations/meta/0051_snapshot.json
• packages/db/src/migrations/meta/_journal.json
• packages/db/src/schema.ts
• src/app/admin/api/users/[id]/dev/insert-usage-record/route.ts
• src/lib/processUsage.ts
• src/lib/processUsage.types.ts
• src/scripts/usage/benchmark-insert-usage.ts
• src/tests/helpers/microdollar-usage.helper.ts

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_{Reviewed by gpt-5.4-20260305 · 675,749 tokens}