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/LearningDashboard/Show.hs

@@ -2,6 +2,7 @@ module Web.View.LearningDashboard.Show where
 
 import Web.View.Prelude
 import Data.Time (diffUTCTime, getCurrentTime, nominalDay)
+import qualified Data.Text as T
 
 data ShowView = ShowView
     { topCorrelations     :: ![OutcomeCorrelation]
@@ -159,7 +160,7 @@ renderKnowledge e = [hsx|
     <div>
         <a href={ShowInstitutionalKnowledgeAction (e.id)}
            class="text-sm text-blue-600 hover:underline">
-            {take 80 e.summary <> if length e.summary > 80 then "…" else ""}
+            {T.take 80 e.summary <> if T.length e.summary > 80 then "…" else ""}
         </a>
     </div>
 |]