fix(data-export): handle bigint hourly cursors

[pandemicsyn]

Summary

• Normalize PostgreSQL integer values returned as string, number, or bigint when exporting microdollar_usage_hourly.
• Preserve the hourly source's numeric SQL ordering and expression-index predicates while converting exported country IDs and keyset cursors to stable strings.
• Add regression coverage for the shared node-postgres INT8 parser returning both a real country ID and the null sentinel as JavaScript bigint values.

Verification

• The production warehouse query was run manually for an affected personal export and returned hourly rows with bigint-backed country IDs and -1 null sentinels.
• End-to-end export verification requires deployment because the failure occurs with the production Hyperdrive and shared node-postgres type parser.

Visual Changes

N/A

Reviewer Notes

• The previous mapper accepted only number and string, but @kilocode/db/client globally parses PostgreSQL INT8 as JavaScript bigint. This caused every observed hourly source read to fail after a successful database query.
• The SQL is intentionally unchanged so ORDER BY COALESCE(vercel_ip_country_id, -1) continues to match the warehouse expression indexes.

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Executive Summary

Reviewed the hourly bigint cursor/country-id normalization and matching tests; the mapper now accepts the shared INT8 parser’s bigint values without changing SQL ordering or index predicates.

Files Reviewed (2 files)

• services/user-data-export/src/source-adapters.ts
• services/user-data-export/src/source-adapters.test.ts

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_{Review guidance: REVIEW.md from base branch main}