fix: consolidate transaction hash to single canonical column

[EmeditWeb]

Problem

Transactions service (lines 216-251) handles both hash and transaction_hash columns. This dual-column handling should be resolved with a migration.

What To Build

1. Run migration to unify column name
2. Remove dual-column handling code
3. Update all references

Files To Touch

• src/modules/transactions/transactions.service.ts — lines 216-251

Acceptance Criteria

• Single column for transaction hash
• Migration script exists
• Build passes

Mandatory Checks

• context/ files read
• npm run build passes
• PR references this issue

[anidroid1184]

Hi! I would like to apply for this issue to unify the transaction hash column and remove the dual-column technical debt. This will be one of my first open-source contributions, and I am excited to help clean up the API codebase!

My approach for this issue will be:

1. Create a dedicated branch: fix/unify-transaction-hash-column.
2. Generate a new database migration using the Supabase CLI (supabase migration new) to safely rename or unify the hash column into transaction_hash in the remote/local schema.
3. Clean up src/modules/transactions/transactions.service.ts (lines 216-251) by removing the fallback block (legacyHashPayload and the error sniffing logic), leaving a clean, single insert statement using transaction_hash.
4. Run npm run build and npm run test to verify that all references are updated and the project builds successfully.

I am ready to start as soon as you can assign this to me!