feat: catch-all page for stopped apps, deploy controls, dashboard open button

Stopped/undeployed app subdomains now show a branded page instead of
Traefik 404. Deploy settings page gains start/stop/restart controls.
Dashboard shows "Megnyitás" button for running apps.

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

controller/internal/web/handlers.go

@@ -171,6 +171,21 @@ func (s *Server) dashboardHandler(w http.ResponseWriter, r *http.Request) {
 		data["CrossDriveFailed"] = crossDriveFailed
 	}
 
+	// Build subdomain map for "Megnyitás" buttons
+	subdomains := make(map[string]string)
+	for _, stack := range deployedStacks {
+		if stack.Deployed {
+			if appCfg := s.stackMgr.LoadAppConfigByName(stack.Name); appCfg != nil {
+				if sd, ok := appCfg.Env["SUBDOMAIN"]; ok && sd != "" {
+					subdomains[stack.Name] = sd
+					continue
+				}
+			}
+		}
+		subdomains[stack.Name] = stack.Meta.Subdomain
+	}
+	data["Subdomains"] = subdomains
+
 	if s.alertManager != nil {
 		data["DiskWarnings"] = s.alertManager.GetInlineAlerts("dashboard")
 	}
@@ -303,6 +318,13 @@ func (s *Server) deployHandler(w http.ResponseWriter, r *http.Request, name stri
 	}
 	data["StoragePaths"] = deployPaths
 
+	// Effective subdomain for "Megnyitás" button
+	if alreadyDeployed && appCfg != nil {
+		if sd, ok := appCfg.Env["SUBDOMAIN"]; ok && sd != "" {
+			data["EffectiveSubdomain"] = sd
+		}
+	}
+
 	// Storage info for already-deployed apps with HDD data
 	if alreadyDeployed {
 		storageInfo := s.storageInfoForStack(name)