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>

.claude/rules/docker-orchestration.md

@@ -49,7 +49,7 @@ Traffic routing is implicit: Traefik labels (`cameleer.app`, `cameleer.environme
 
 **Deploy stages** (`DeployStage`): PRE_FLIGHT -> PULL_IMAGE -> CREATE_NETWORK -> START_REPLICAS -> HEALTH_CHECK -> SWAP_TRAFFIC -> COMPLETE (or FAILED at any stage). Rolling reuses the same stage labels inside the per-replica loop; the UI progress bar shows the most recent stage.
 
-**Deployment uniqueness**: `DeploymentService.createDeployment()` deletes any STOPPED/FAILED deployments for the same app+environment before creating a new one, preventing duplicate rows.
+**Deployment retention**: `DeploymentService.createDeployment()` deletes FAILED deployments for the same app+environment before creating a new one, preventing failed-attempt buildup. STOPPED deployments are preserved as restorable checkpoints — the UI Checkpoints disclosure lists every deployment with a non-null `deployed_config_snapshot` (RUNNING, DEGRADED, STOPPED) minus the current one.
 
 ## JAR Management