panel: place drill-down back links under the heading

The user form had Back to users at the bottom of the card; all drill-down
pages now use a shared back_link template with a structural test.

Co-Authored-By: Claude <Composer 2.5> <noreply@anthropic.com>
Co-authored-by: Cursor <cursoragent@cursor.com>

internal/web/view/view.go

@@ -65,7 +65,7 @@ func New(version string) (*Engine, error) {
 	}
 	for name, files := range pageFiles {
 		patterns := append([]string{"templates/layout.html"}, files...)
-		tmpl, err := template.New("layout.html").ParseFS(assetsFS, patterns...)
+		tmpl, err := template.New("layout.html").Funcs(templateFuncs()).ParseFS(assetsFS, patterns...)
 		if err != nil {
 			return nil, fmt.Errorf("parse template %s: %w", name, err)
 		}
@@ -81,6 +81,17 @@ func New(version string) (*Engine, error) {
 	return e, nil
 }
 
+// templateFuncs supplies helpers shared across page templates.
+func templateFuncs() template.FuncMap {
+	return template.FuncMap{
+		// back builds the map back_link reads; keeps href and label paired at
+		// the call site instead of repeating the <a class="back"> markup.
+		"back": func(href, label string) map[string]string {
+			return map[string]string{"Href": href, "Label": label}
+		},
+	}
+}
+
 // Page returns a parsed page template by logical name. It is exported for
 // template guard tests that assert structural properties across all pages.
 func (e *Engine) Page(name string) *template.Template {