feat: close preprod observability loop

deploy/observability/caddy/grafana.Caddyfile

@@ -0,0 +1,13 @@
+# Optional Caddy snippet for exposing Grafana through a protected hostname.
+# Generate a password hash with:
+# caddy hash-password --plaintext '<password>'
+
+{$OBSERVABILITY_HOST} {
+	encode gzip zstd
+
+	basicauth {
+		{$GRAFANA_BASIC_AUTH_USER} {$GRAFANA_BASIC_AUTH_HASH}
+	}
+
+	reverse_proxy grafana:3000
+}