feat: integrate Sentry for error tracking and fix metrics DI startup …

[Truphile]

Closes #12

I have completed the task successfully. Here is a summary of the work:

1. Sentry Initialization:
   • Initialized Sentry via Sentry.init at the very top of main.ts, ensuring it runs before NestJS
   bootstraps.
   • Used process.env.SENTRY_TRACES_SAMPLE_RATE to support configuring the trace sample rate via environment
   variables (falling back to 0.1 as requested).
   • Configured process.env.SENTRY_DSN as an optional fallback ( process.env.SENTRY_DSN || undefined ) to
   ensure the application starts up gracefully as a no-op fallback when SENTRY_DSN is empty.

2. NestJS Setup & Sentry Module:
   • Registered SentryModule.forRoot() in the imports list in app.module.ts.
   • Registered the SentryGlobalFilter globally as APP_FILTER under the providers array in app.module.ts,
   enabling all unhandled controller exceptions to be caught and logged directly to Sentry.

3. Validation & Test Route:
   • Added a sentry-test endpoint to the HealthController in health.controller.ts which throws a deliberate
   error
   ( throw new Error('sentry test') ).
   • Decorated the endpoint with full Swagger @apioperation and @apiresponse decorators to conform to our
   standards, with no any types introduced.
   • Tested the endpoint locally and confirmed that unhandled exceptions are caught by the Sentry filter and
   logged.

4. Environment Template:
   • Created the .env.example configuration template containing environment variable definitions, adding
   SENTRY_DSN= and SENTRY_TRACES_SAMPLE_RATE=0.1 , alongside other project variables.

5. Fixed Pre-existing DI Bug:
   • Resolved a pre-existing DI error in the codebase's prometheus metrics setup which had prevented the
   application from starting:
   • Updated metrics.service.ts to use @InjectMetric(...) instead of Nest's generic @Inject(...) to allow
   @willsoto/nestjs-prometheus to correctly resolve the metric tokens.
   • Decorated MetricsModule with @global() in metrics.module.ts so that the MetricsService provider is
   globally accessible.
   • Removed MetricsController from the duplicate declaration in the controllers array in
   metrics.module.ts
   to avoid duplicated route binding errors in Fastify.

6. Documentation & Progress tracking:
   • Added a section "Error tracking" in README.md documenting how to enable and configure Sentry.
   • Logged the work inside the progress-tracker.md file.
   • Verified that npm run build compiles with zero compiler warnings or errors.