[RELIABILITY][EXPORTS] Stream paginated report exports instead of materializing entire datasets

[Obiajulu-gif]

Summary

Report and ledger exports build complete query results and CSV line arrays in memory. Data growth can exhaust serverless memory or time limits and produce partial operator downloads.

Repository evidence

• app/api/admin/reports/export/route.ts materializes report datasets before calling toCsv.
• app/api/transactions/ledger/export/route.ts and lib/security/audit-export.ts accumulate full row arrays/strings.

Scope

• Page through stable sort keys and stream CSV with backpressure.
• Set explicit row/time budgets and return an async export job for oversized requests if needed.
• Record export status, row count, checksum, and terminal failure.

Acceptance criteria

• Peak memory is bounded independently of export row count.
• Rows are neither duplicated nor skipped under the documented snapshot policy.
• Interrupted exports fail visibly and never appear complete.

Tests

• Large-dataset memory/backpressure test.
• Pagination boundary, concurrent-write snapshot, disconnect, and checksum tests.

Non-goals

• Adding new report fields or changing CSV formula-safety behavior.

[muokwejosh-cloud]

I’ve reviewed the issue details and documentation, and I understand the problem statement and expected outcome. Please assign this task to me — I’m ready to start working on it.

[grantfox-oss]

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Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #182)
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[grantfox-oss]

🎉 This issue has been marked as completed on GrantFox as part of the Third Campaign campaign!

@muokwejosh-cloud's PR #204 was approved and merged by @Obiajulu-gif.

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