[Backend] Two different withTransaction helpers exist with different retry semantics

[grantfox-oss]

Telegram (ask questions / claim the issue here first): https://t.me/+DOylgFv1jyJlNzM0

Why this matters

src/db/connection.ts exports a withTransaction with transient-error retry and exponential backoff, while src/db/transaction.ts exports a separate withTransaction with no retries; importing the wrong one silently drops deadlock/serialization retry behavior on money-moving transactions.

Acceptance criteria

• Consolidate to a single withTransaction (or clearly distinct names like withTransaction vs withTransactionNoRetry)
• Update all imports to the canonical helper
• Ensure money-moving paths use the retrying variant
• Document the choice in the db module

Files to touch

• src/db/connection.ts
• src/db/transaction.ts

Out of scope

• Changing isolation levels
• Adding savepoint support

[Peolite001]

I would love to work on this issue

[binayyub4211]

Hey maintainer Can you please assign me to work on this issue

[grantfox-oss]

🦊 GrantFox — @Peolite001 has been assigned to this issue as part of the Official Campaign campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #20)
2. Your PR will be reviewed by the LabsCrypt maintainers

Good luck! Track your progress on GrantFox.