fix(WP-0017/E3): Layer 3 error fixes — controllers and views

Fix compilation errors across 6 controllers and 29 views: import cleanup,
ResponseException pattern for API auth, type fixes, unused import removal.

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

Web/View/StaticPages/Tutorial.hs

@@ -25,7 +25,7 @@ instance View TutorialView where
                 </p>
                 <div class="bg-gray-900 rounded-lg p-4 text-sm font-mono text-green-400">
                     <div class="text-gray-400 mb-1">-- Every rendered widget wraps its HSX in widgetEnvelope</div>
-                    widgetEnvelope widgetId viewContext [hsx|...|]
+                    {"widgetEnvelope widgetId viewContext [hsx|...|]" :: Text}
                 </div>
                 <p class="text-sm text-gray-500 mt-2">
                     The envelope injects <code>data-widget-id</code> and <code>data-view-context</code> attributes,