fix: resolve bigint timestamps and event upsert race conditions

[chizzy192]

closes #830 closes #831

Description

This commit resolves two issues:

1. Migrates time-valued fields (startTime, lastUpdateTime, endTime, pausedAt, StreamEvent.timestamp) from Int to BigInt to prevent 2038 overflow (and early overflow on long-duration streams).
2. Prevents unique constraint / write-race collisions between action controllers and the indexer worker on StreamEvent records by using upsert in controllers, and conditional updates in the worker when a placeholder event exists.

Type of Change

• 🐛 Bug fix (non-breaking change which fixes an issue)
• 🧪 Test addition or update

Related Issues

Closes #830
Closes #831

Changes Made

• Modified backend/prisma/schema.prisma to change time columns to BigInt.
• Added database migration bigint_timestamps.
• Added global BigInt JSON serializer to backend/src/app.ts.
• Updated ClaimableStreamState in claimable.service.ts and updated calculations to support bigint.
• Modified withdraw, pause, resume controllers to use upsert and pass BigInt values.
• Updated indexer worker event handlers to conditionally update ledgerSequence/timestamp on existing placeholder records.
• Updated unit and integration tests to mock and expect upsert.
• Fixed sunset/deprecated route tests.

Testing

• Unit tests added/updated
• Integration tests added/updated

Test Steps

1. Run DATABASE_URL=postgresql://flowfi:flowfi_dev_password@127.0.0.1:5433/flowfi npm test

Description

Type of Change

• 🐛 Bug fix (non-breaking change which fixes an issue)
• ✨ New feature (non-breaking change which adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to not work as expected)
• 📚 Documentation update
• 🔧 Refactoring (no functional changes)
• ⚡ Performance improvement
• 🧪 Test addition or update

Related Issues

Closes #

Changes Made

Testing

Test Coverage

• Unit tests added/updated
• Integration tests added/updated
• Manual testing performed

Test Steps

Breaking Changes

Breaking Changes:

Migration Guide:

Screenshots/Demo

Checklist

• My code follows the project's style guidelines
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published
• I have checked for breaking changes and documented them if applicable

Additional Notes

[ogazboiz]

heads up: main's ci was broken (the Backend CI and Backend Docker Image CI jobs) until the fixes in #969 and #974 just landed, so the red backend/docker checks on this pr are almost certainly stale, they ran against the broken main. please rebase to re-test against the now-green main: git fetch origin && git rebase origin/main && git push --force-with-lease. once it's green i'll review and merge. (if a non-backend check like Frontend CI is still red after the rebase, that part is a real issue worth a look, since frontend ci was passing on main.)

[ogazboiz]

the bigint-timestamp + sqlite->postgres migration conversion + the event-upsert race fix look legit, and the only red is the Docker Image CI at the container health-check step ('could not find prisma schema'), which is known infra noise, not your code, everything else passes. please rebase/re-run against the current green main, and if the Docker step still fails after that i'll dig in: git fetch origin && git rebase origin/main && git push --force-with-lease.