feat: API monitoring

[wylited]

How this monitoring system will work is that each API service will expose a fastify-metrics endpoint at /metrics, which requires a prometheus key to access.
this is a Prometheus scrapable endpoint for our monitoring platform.

Furthermore, if provided, it will fastify will log automatically to a Loki logging server using pino-loki.

The rest of the setup for monitoring will be done on the usthing server.

[Copilot]

Pull request overview

This PR adds API monitoring capabilities to the template API service by integrating Prometheus metrics collection via fastify-metrics and optional Loki logging via pino-loki. The metrics endpoint can be optionally protected with a bearer token for security.

Changes:

• Added fastify-metrics and pino-loki dependencies for monitoring and logging
• Implemented configurable Loki transport for centralized logging
• Created /metrics endpoint with optional authentication via PROMETHEUS_KEY
• Updated test helper to support passing custom options for testing different configurations

Reviewed changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
yarn.lock	Added dependencies for fastify-metrics, pino-loki, prom-client, and related packages
package.json	Added fastify-metrics and pino-loki to dependencies
src/app.ts	Implemented Loki transport configuration, metrics endpoint with optional authentication
test/helper.ts	Modified build function to accept optional AppOptions for flexible testing
test/routes/metrics.test.ts	Added comprehensive tests for metrics endpoint with and without authentication

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[polyipseity]

Reviewed! Once you address the two minor issues by yourself, you can merge it.