Fix API markets timeout issue

[MKNas01]

Description

Closes #396

This PR implements a per-request graceful timeout on the /api/markets endpoints to fulfill the backend requirements for the GrantFox FWC26 campaign (Stellar Wave).

Changes Made

• Middleware: Created requestTimeout in src/middleware/timeout.ts utilizing AbortController to gracefully terminate requests exceeding the limit (set to 10 seconds).
• Routing: Applied the timeout middleware to marketsRouter immediately following the rate limiters.
• Logging & Errors: Integrated structured logging (logger.warn) capturing the correlationId and returning a standardized 408 Request Timeout error envelope when triggered.
• Testing: Added focused unit tests for the middleware and an integration test verifying the 408 response on delayed queries. Minimum 90% coverage achieved on changed lines.
• Documentation: Updated docs/markets-api.md to reflect the new 408 timeout error visibility.

Acceptance Criteria Checklist

• Implementation matches the description (per-request timeout with graceful abort).
• Tests added and passing (unit + edge cases covered).
• Docs updated.
• Adheres to repo's lint, standardized error envelope, and structured logging guidelines.

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[greatest0fallt1me]

Merged via direct push to main (admin)