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/Controller/Requirements.hs

@@ -6,6 +6,7 @@ import Web.View.Requirements.Show
 import Generated.Types
 import IHP.Prelude
 import IHP.ControllerPrelude
+import Web.Routes ()
 
 instance Controller RequirementsController where
     beforeAction = ensureIsUser