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

frontend/src/components/EditorLayout/hooks/useSidebarContextMenu.test.ts

@@ -18,6 +18,7 @@ function makeOptions(
   const stackListState = {
     stackStatuses,
     stackPorts,
+    stackSelfFlags: {},
     isStackBusy: () => false,
     isPinned: () => false,
     labels: [],