feat: add Prometheus docker_sd_configs labels to agent containers

Labels prometheus.scrape, prometheus.path, and prometheus.port are now
set on every deployed container based on the resolved runtime type,
enabling automatic Prometheus service discovery via docker_sd_configs.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

cameleer3-server-app/src/main/java/com/cameleer3/server/app/runtime/DeploymentExecutor.java

@@ -162,6 +162,7 @@ public class DeploymentExecutor {
 
             Map<String, String> baseEnvVars = buildEnvVars(app, env, config);
             Map<String, String> labels = TraefikLabelBuilder.build(app.slug(), env.slug(), tenantId, config);
+            labels.putAll(PrometheusLabelBuilder.build(resolvedRuntimeType));
 
             List<Map<String, Object>> replicaStates = new ArrayList<>();
             List<String> newContainerIds = new ArrayList<>();

cameleer3-server-app/src/main/java/com/cameleer3/server/app/runtime/PrometheusLabelBuilder.java

@@ -0,0 +1,35 @@
+package com.cameleer3.server.app.runtime;
+
+import java.util.LinkedHashMap;
+import java.util.Map;
+
+public final class PrometheusLabelBuilder {
+
+    private PrometheusLabelBuilder() {}
+
+    public static Map<String, String> build(String resolvedRuntimeType) {
+        Map<String, String> labels = new LinkedHashMap<>();
+        labels.put("prometheus.scrape", "true");
+
+        switch (resolvedRuntimeType) {
+            case "spring-boot" -> {
+                labels.put("prometheus.path", "/actuator/prometheus");
+                labels.put("prometheus.port", "8081");
+            }
+            case "quarkus", "native" -> {
+                labels.put("prometheus.path", "/q/metrics");
+                labels.put("prometheus.port", "9000");
+            }
+            case "plain-java" -> {
+                labels.put("prometheus.path", "/metrics");
+                labels.put("prometheus.port", "9464");
+            }
+            default -> {
+                labels.put("prometheus.path", "/actuator/prometheus");
+                labels.put("prometheus.port", "8081");
+            }
+        }
+
+        return labels;
+    }
+}

cameleer3-server-app/src/test/java/com/cameleer3/server/app/runtime/PrometheusLabelBuilderTest.java

@@ -0,0 +1,50 @@
+package com.cameleer3.server.app.runtime;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.Map;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class PrometheusLabelBuilderTest {
+
+    @Test
+    void springBootLabels() {
+        Map<String, String> labels = PrometheusLabelBuilder.build("spring-boot");
+        assertEquals("true", labels.get("prometheus.scrape"));
+        assertEquals("/actuator/prometheus", labels.get("prometheus.path"));
+        assertEquals("8081", labels.get("prometheus.port"));
+    }
+
+    @Test
+    void quarkusLabels() {
+        Map<String, String> labels = PrometheusLabelBuilder.build("quarkus");
+        assertEquals("true", labels.get("prometheus.scrape"));
+        assertEquals("/q/metrics", labels.get("prometheus.path"));
+        assertEquals("9000", labels.get("prometheus.port"));
+    }
+
+    @Test
+    void nativeLabels() {
+        Map<String, String> labels = PrometheusLabelBuilder.build("native");
+        assertEquals("true", labels.get("prometheus.scrape"));
+        assertEquals("/q/metrics", labels.get("prometheus.path"));
+        assertEquals("9000", labels.get("prometheus.port"));
+    }
+
+    @Test
+    void plainJavaLabels() {
+        Map<String, String> labels = PrometheusLabelBuilder.build("plain-java");
+        assertEquals("true", labels.get("prometheus.scrape"));
+        assertEquals("/metrics", labels.get("prometheus.path"));
+        assertEquals("9464", labels.get("prometheus.port"));
+    }
+
+    @Test
+    void unknownDefaultsToSpringBoot() {
+        Map<String, String> labels = PrometheusLabelBuilder.build("unknown");
+        assertEquals("true", labels.get("prometheus.scrape"));
+        assertEquals("/actuator/prometheus", labels.get("prometheus.path"));
+        assertEquals("8081", labels.get("prometheus.port"));
+    }
+}