feat: block self-stack lifecycle ops with UI and preflight guardrails (#1569)

* feat: block self-stack lifecycle ops with UI and preflight guardrails

Refuse update, deploy, down, stop, and delete when the stack matches Sencho's compose project.

Return 409 self_stack_protected. Expose isSelf on /statuses and disable guarded UI actions.

Add SelfStackProtectedDialog and self-managed-stack preflight warning.

Closes #1564

* fix: add missing stackSelfFlags mock to useSidebarContextMenu test

The production hook now reads stackListState.stackSelfFlags[file], but the
test mock did not include it, causing 6 tests to fail with TypeError:
Cannot read properties of undefined (reading 'web.yml').

* fix: harden self-stack protection during startup

Add a global environment preflight warning when Sencho is managed inside COMPOSE_DIR.

Align status decoration and route guards on Docker label fallback detection.

Block rollback and service-level stop on the protected self stack.

* fix: add self_stack_location to diagnostics-route expected check IDs

backend/src/services/DockerController.ts

@@ -104,6 +104,8 @@ export interface BulkStackInfo {
   running?: number;
   /** Total container count for the stack; paired with `running` for the sidebar tooltip. */
   total?: number;
+  /** True when this stack is the running Sencho instance (compose project matches stack name). */
+  isSelf?: boolean;
 }
 
 export interface ClassifiedImage {