feat(metrics): add Prometheus metrics support with endpoint and configuration

[matheusandre1]

• 🐛 Bug fix
• ✨ Feature
• 📝 Documentation
• 🔧 Refactor
• 🚀 Performance
• ✅ Test
• 🔒 Security
• 📦 Dependency update
• 🏗️ CI/CD
• [ ]

Related Issues

Closes: #44

Checklist

• My code follows the project's coding standards
• I have performed a self-review of my own code
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have updated the documentation accordingly
• My changes generate no new warnings or errors

[thrillhousebot]

🤖 ThrillhouseBot PR Summary

What this PR does

Adds a GET /metrics endpoint serving OpenTelemetry metrics in Prometheus text format, along with a new counter for completed/failed reviews, configuration for enabling/disabling, and integration tests.

Control-Flow Diagram

🔀 Show diagram

flowchart TD
  A["ReviewOrchestrator.applyReviewResult()"] --> B["ReviewOutcomeMetrics.recordCompleted()"]
  A2["ReviewOrchestrator.applyReviewFailure()"] --> B2["ReviewOutcomeMetrics.recordFailed()"]
  C["HTTP GET /metrics"] --> D["PrometheusMetricsResource.scrape()"]
  D --> E{"reader present?"}
  E -- yes --> F["collect and write Prometheus format"]
  E -- no --> G["return 404"]

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Changes Overview

• Files changed: 14
• Lines added: +439
• Lines removed: -2

Changed Files

File	Change	Summary
.env.example	Modified	Added commented OTEL_EXPORTER_ENDPOINT and PROMETHEUS_METRICS_ENABLED with guidance.
CHANGELOG.md	Modified	Added entry for Prometheus metrics endpoint.
README.md	Modified	Updated documentation for new config keys and Prometheus endpoint.
src/main/java/dev/thiagogonzaga/thrillhousebot/config/ThrillhouseConfig.java	Modified	Added MetricsConfig sub-interface with prometheus-enabled flag.
src/main/java/dev/thiagogonzaga/thrillhousebot/observability/PrometheusMetricsRegistrar.java	Added	CDI bean that conditionally registers a PrometheusMetricReader with the OTel SDK; provides optional reader for the scrape endpoint.
src/main/java/dev/thiagogonzaga/thrillhousebot/observability/PrometheusMetricsResource.java	Added	JAX-RS resource exposing GET /metrics that returns Prometheus text format or 404 if disabled.
src/main/java/dev/thiagogonzaga/thrillhousebot/observability/ReviewOutcomeMetrics.java	Added	Application-scoped bean recording a counter for completed/failed reviews via OpenTelemetry.
src/main/java/dev/thiagogonzaga/thrillhousebot/review/ReviewOrchestrator.java	Modified	Inject ReviewOutcomeMetrics and record completed/failed outcomes after review result application.
src/main/resources/application.properties	Modified	Enable OpenTelemetry metrics export and define thrillhousebot.metrics.prometheus-enabled property.
src/test/java/dev/thiagogonzaga/thrillhousebot/observability/PrometheusMetricsEndpointDisabledTest.java	Added	Integration test confirming /metrics returns 404 when OTel SDK is disabled.
src/test/java/dev/thiagogonzaga/thrillhousebot/observability/PrometheusMetricsEndpointTest.java	Added	Quarkus integration test that starts app with SDK enabled and asserts /metrics returns recorded metrics.
src/test/java/dev/thiagogonzaga/thrillhousebot/observability/PrometheusMetricsResourceTest.java	Added	Unit test exercising registrar and resource against a real OpenTelemetry SDK; verifies Prometheus text output.
src/test/java/dev/thiagogonzaga/thrillhousebot/review/ReviewOrchestratorTest.java	Modified	Inject no-op ReviewOutcomeMetrics to satisfy new constructor parameter.

…and 1 more file(s).

Risk Assessment

Risk	Count
🔴 Critical	0
🟠 High	0
🟡 Medium	0
🔵 Low	0

No new issues found in this PR, but the review cannot be approved until required CI is confirmed green.

⚠️ Required CI Checks Status

Some required checks are still pending or have failed:

Check	Type	Status	Detail
format	missing	⏳ Pending	-
test	missing	⏳ Pending	-
frontend	missing	⏳ Pending	-
trivy	missing	⏳ Pending	-
dependency-review	missing	⏳ Pending	-

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