Add a consistency test asserting `POST /api/v1/quote` rejects a non-positive `amount` with the same 400 envelope shape as `routes/liquidity.ts`

[Jagadeeshftw]

📌 Description

QuoteService.quote, LiquidityService.addLiquidity, and SettlementService.open all funnel through the same requirePositiveNumber helper for their amount field, so their 400 responses for a non-positive amount should be identical in shape and message pattern. There doesn't appear to be a cross-route consistency test proving this — a future change to just one call site's error handling could silently diverge without any test catching it.

🧩 Requirements and context

• Add a table-driven test issuing a non-positive (0, -1) amount to POST /api/v1/quote, POST /api/v1/liquidity, and POST /api/v1/settlements, asserting all three return 400 with the same error.code (BAD_REQUEST) and a message referencing "amount".

🛠️ Suggested execution

• Add the cross-route test, likely as a new test file (e.g. src/routes/amountValidationConsistency.test.ts) or appended to an existing shared test setup, exercising all three routes via supertest against createApp().

✅ Acceptance criteria

• New test passes, demonstrating consistent 400 behavior for non-positive amount across all three routes.
• No production code changes expected unless an inconsistency is actually found, in which case the diverging call site is fixed to match.

🔒 Security notes

N/A — test-only; guards a cross-cutting validation consistency invariant relevant to defensive input handling.

📋 Guidelines

• Minimum 95% test coverage
• Clear documentation
• Timeframe: 96 hours