feat(monitoring): add Prometheus metrics endpoint and Grafana dashboards

Add observability stack with @willsoto/nestjs-prometheus for /metrics endpoint,
Prometheus scraping config, and 4 auto-provisioned Grafana dashboards
(API overview, database, search, business metrics).

Co-Authored-By: Paperclip <noreply@paperclip.ing>

monitoring/prometheus/prometheus.yml

@@ -0,0 +1,16 @@
+global:
+  scrape_interval: 15s
+  evaluation_interval: 15s
+
+scrape_configs:
+  - job_name: 'goodgo-api'
+    metrics_path: '/metrics'
+    static_configs:
+      - targets: ['host.docker.internal:3001']
+        labels:
+          service: 'goodgo-api'
+          environment: 'development'
+
+  - job_name: 'prometheus'
+    static_configs:
+      - targets: ['localhost:9090']