fix(WP-0016): Layer 3 compilation fixes — Sessions auth, Widgets import consolidation, Scientific type

- Sessions: replace raw authenticate/unsetSession with IHP login/logout/verifyPassword
- Widgets/New, Widgets/Show: consolidate imports to Web.View.Prelude
- Widgets/Show: unwrap Id newtype for childrenOf comparison, Double → Scientific in renderSignalValue

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

Web/Controller/Sessions.hs

@@ -4,7 +4,8 @@ import Web.Types
 import Web.View.Sessions.New
 import Generated.Types
 import IHP.LoginSupport.Helper.Controller
-import IHP.AuthSupport.Controller.Sessions (SessionsControllerConfig)
+import IHP.AuthSupport.Controller.Sessions (SessionsControllerConfig (..))
+import IHP.AuthSupport.Authentication (verifyPassword)
 import IHP.Prelude
 import IHP.ControllerPrelude
 
@@ -14,17 +15,20 @@ instance Controller SessionsController where
         render NewView { user }
 
     action CreateSessionAction = do
-        (user, token) <- authenticate @User
-        case user of
-            Just user -> do
-                setSession "userId" (show user.id)
+        maybeUser <- query @User
+            |> filterWhere (#email, param "email")
+            |> fetchOneOrNothing
+        case maybeUser of
+            Just user | verifyPassword user (param "password") -> do
+                login user
                 redirectTo HubsAction
-            Nothing -> do
+            _ -> do
                 setErrorMessage "Invalid email or password"
                 redirectTo NewSessionAction
 
     action DeleteSessionAction = do
-        unsetSession "userId"
-        redirectTo NewSessionAction
+        currentUserOrNothing @User >>= \case
+            Just user -> logout user >> redirectTo NewSessionAction
+            Nothing   -> redirectTo NewSessionAction
 
 instance SessionsControllerConfig User