feat(license): surface execution/log/metric retention days on Environment

Adds three int fields to the Environment record + repository row mapper,
matching the columns added in V5. Default value is 1 per the V5 NOT NULL
DEFAULT 1. Read DTO surfaces the fields via Jackson record serialization;
setter endpoint deferred to a follow-up that wires the corresponding
license cap checks.

The canonical constructor enforces >= 1 for each retention field — V5
guarantees this at the DB level, but the runtime guard catches in-memory
construction errors (e.g., test sites that pass 0).

Test sites updated to the 12-arg signature with retention defaults of 1.
EnvironmentAdminControllerIT gains a regression test asserting the wire
shape exposes all three fields.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

cameleer-server-core/src/main/java/com/cameleer/server/core/runtime/Environment.java

@@ -13,5 +13,23 @@ public record Environment(
         Map<String, Object> defaultContainerConfig,
         Integer jarRetentionCount,
         String color,
-        Instant createdAt
-) {}
+        Instant createdAt,
+        int executionRetentionDays,
+        int logRetentionDays,
+        int metricRetentionDays
+) {
+    public Environment {
+        if (executionRetentionDays < 1) {
+            throw new IllegalArgumentException(
+                    "executionRetentionDays must be >= 1 (got " + executionRetentionDays + ")");
+        }
+        if (logRetentionDays < 1) {
+            throw new IllegalArgumentException(
+                    "logRetentionDays must be >= 1 (got " + logRetentionDays + ")");
+        }
+        if (metricRetentionDays < 1) {
+            throw new IllegalArgumentException(
+                    "metricRetentionDays must be >= 1 (got " + metricRetentionDays + ")");
+        }
+    }
+}