Refactor/detail route modular

lib/app/models/task_attribute.dart

@@ -0,0 +1,25 @@
+/// Task attributes shown on the detail page, in display order.
+///
+/// [name] is the Taskwarrior field name, used both as the on-screen label and
+/// as the key passed to `Modify.set`.
+enum TaskAttribute {
+  description,
+  status,
+  entry,
+  modified,
+  start,
+  end,
+  due,
+  wait,
+  until,
+  priority,
+  project,
+  tags,
+  urgency;
+
+  /// Attributes that are only ever displayed, never edited.
+  bool get isDisplayOnly =>
+      this == TaskAttribute.entry ||
+      this == TaskAttribute.modified ||
+      this == TaskAttribute.urgency;
+}