feat(routes-f): implement audit trail endpoint with cursor pagination

[Robinsonchiziterem]

Description
Closes #284

Changes proposed
What were you told to do?
Backend: Implement routes-f audit trail endpoint.

What did you do?
I exposed a read-only endpoint to fetch audit events for Routes-F activities with the following changes:

Data Models: Added the
AuditEvent
interface and updated
MetricsKey
to include audit in
lib/routes-f/types.ts
.
Core Logic: Updated
lib/routes-f/store.ts
to include stable mock audit events and implemented a
getAuditTrail
function with cursor-based pagination (descending order).
Infrastructure: Updated
lib/routes-f/metrics.ts
to register and track the new audit metric.
API Endpoint: Created GET /api/routes-f/audit in
app/api/routes-f/audit/route.ts
with support for limit and cursor parameters, including rate limiting and metrics recording.
Testing: Added a comprehensive test suite in
app/api/routes-f/
tests
/audit.test.ts
covering ordering, pagination limits, and empty state behavior.
Check List (Check all the applicable boxes)
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Screenshots/Videos

NOTE

The pagination logic has been verified via the included unit tests. Below is an example of the API response structure:

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