feat: add service-scoped Compose update and restore (#1648)

* feat: add service-scoped Compose update and restore

Allow updating or rebuilding one declared Compose service on multi-service
stacks without recreating siblings, with recovery snapshots, health-gate
observation, and prune holds for rollback images. Full-stack update paths
and single-service UX stay unchanged.

* fix: sanitize service-scoped update log messages for CodeQL

* fix: address service-scoped update audit findings B-01 through B-07

* fix: complete service-scoped update audit metadata and surfaces

* test: wrap Updates readiness tests for deploy-feedback context

* fix: keep service recovery reachable without Deploy Progress

Make failed service-gate recovery discoverable when Deploy Progress is
disabled or dismissed, suppress stale image-scan notification side
effects, normalize ComposeService line endings, and add focused
regression coverage.

* fix: resurface ContainersHealth density and expand on multi-service stacks

Service grouping hid the summary strip and Compact/Detailed/Expand controls that still applied to multi-container stacks.

backend/src/services/GitSourceService.ts

@@ -1337,7 +1337,7 @@ export class GitSourceService {
                     console.warn(`[GitSource] ${busy}`);
                     return { applied: true, deployed: false, deployError: busy };
                 }
-                HealthGateService.getInstance().begin(nodeId, stackName, 'deploy', 'system:git-source');
+                HealthGateService.getInstance().beginStack(nodeId, stackName, 'deploy', 'system:git-source');
                 console.log(`[GitSource] Applied and deployed ${stackName} at ${commitSha.slice(0, 7)}`);
                 return { applied: true, deployed: true };
             } catch (e) {