fix(deploy): Checkpoints — preserve STOPPED history, fix filter + placement

- Backend: rename deleteTerminalByAppAndEnvironment → deleteFailedByAppAndEnvironment.
  STOPPED rows were being wiped on every redeploy, so Checkpoints was always empty.
  Now only FAILED rows are pruned; STOPPED deployments are retained as restorable
  checkpoints (they still carry deployed_config_snapshot from their RUNNING window).
- UI filter: any deployment with a snapshot is a checkpoint (was RUNNING|DEGRADED only,
  which excluded the main case — the previous blue/green deployment now in STOPPED).
- UI placement: Checkpoints disclosure now renders inside IdentitySection, matching
  the design spec.

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

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

@@ -14,5 +14,6 @@ public interface DeploymentRepository {
     void updateStatus(UUID id, DeploymentStatus status, String containerId, String errorMessage);
     void markDeployed(UUID id);
     void markStopped(UUID id);
-    void deleteTerminalByAppAndEnvironment(UUID appId, UUID environmentId);
+    /** Delete FAILED deployments for this (app, env). STOPPED deployments are preserved as checkpoints. */
+    void deleteFailedByAppAndEnvironment(UUID appId, UUID environmentId);
 }

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

@@ -28,7 +28,7 @@ public class DeploymentService {
         Environment env = envService.getById(environmentId);
         String containerName = env.slug() + "-" + app.slug();
 
-        deployRepo.deleteTerminalByAppAndEnvironment(appId, environmentId);
+        deployRepo.deleteFailedByAppAndEnvironment(appId, environmentId);
         UUID deploymentId = deployRepo.create(appId, appVersionId, environmentId, containerName);
         return deployRepo.findById(deploymentId).orElseThrow();
     }