feat: deployed app removal + missing field injection (v0.19.0)

Add "Eltávolítás" to remove deployed (non-orphaned) stacks — reverts
them to "Nincs telepítve" while preserving templates for redeploy.
Modal offers HDD data and backup data cleanup choices.

Auto-inject missing deploy fields (secrets, domains) into existing
app.yaml when templates are updated via sync or on controller startup.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

controller/internal/stacks/manager.go

@@ -108,6 +108,19 @@ func detectComposeCommand() string {
 	return ""
 }
 
+// DeployedStackNames returns the names of all deployed stacks.
+func (m *Manager) DeployedStackNames() []string {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	var names []string
+	for name, stack := range m.stacks {
+		if stack.Deployed {
+			names = append(names, name)
+		}
+	}
+	return names
+}
+
 // ScanStacks discovers all compose stacks in the stacks directory.
 func (m *Manager) ScanStacks() error {
 	m.mu.Lock()