fix: add json template function for post-deploy data embedding

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

controller/internal/web/funcmap.go

@@ -1,6 +1,7 @@
 package web
 
 import (
+	"encoding/json"
 	"fmt"
 	"html/template"
 	"strings"
@@ -324,6 +325,11 @@ func (s *Server) templateFuncMap() template.FuncMap {
 				return status
 			}
 		},
+		// json marshals a value to JSON for embedding in <script> blocks.
+		"json": func(v interface{}) template.JS {
+			b, _ := json.Marshal(v)
+			return template.JS(b)
+		},
 		// pageMatch returns true if currentPage is in the pages slice.
 		// Used to filter page-specific alerts in layout.html.
 		"pageMatch": func(pages []string, currentPage string) bool {