refactor(templates): apply activeClass helper and full-width layout

- Replace inline ternary operators with activeClass helper function
- Change layout containers from max-w-7xl to w-full for full-width design
- Update file path references in error messages for better debugging

templates/utils.go

@@ -0,0 +1,9 @@
+package templates
+
+func activeClass(current, target string) string {
+	base := "block px-4 py-2 rounded-lg "
+	if current == target {
+		return base + "bg-accent text-bg-primary"
+	}
+	return base + "hover:opacity-80"
+}