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

docs/features/stack-management.mdx

@@ -191,6 +191,8 @@ The header answers three questions at a glance:
 
 The action row to the right of the header keeps everyday lifecycle controls visible. The **More actions** overflow holds Rollback, Scan config, and Delete; the next sections cover both surfaces.
 
+If Sencho discovers its own compose project as a stack (because the deployment directory lives inside `COMPOSE_DIR`), that stack is treated as the running Sencho instance: deploy, update, stop, down, and delete are disabled in the UI and refused by the API. Use **Fleet → Node Update** to upgrade Sencho. Compose Doctor flags the condition during preflight.
+
 ### Image source links
 
 Next to the image line is a links button that turns the image reference into somewhere useful to go. It opens a small menu with: