Show one question per card in the take-quiz screen, with prev/next arrows

Replaces the single long scrollable list of every question with one
card at a time plus arrow navigation, so a student's focus stays on
the current question instead of the whole quiz at once.

src/Client/Features/Quizzes/TakeQuiz/State.fs

@@ -53,6 +53,9 @@ let rec update (token: string option) (msg: Msg) (model: Model) : Model * Cmd<Ms
         updated, cmd
     | AnswerSaved _ -> { model with Error = None }, Cmd.none
     | AnswerSaveFailed(_, err) -> { model with Error = Some err }, Cmd.none
+    | GoToQuestion index ->
+        let clamped = index |> max 0 |> min (List.length model.Data.Questions - 1)
+        { model with CurrentIndex = clamped }, Cmd.none
     | Tick ->
         let updated = { model with RemainingSeconds = remainingSeconds model.Data DateTimeOffset.UtcNow }
         // The server is the actual authority (it now rejects any answer

src/Client/Features/Quizzes/TakeQuiz/Types.fs

@@ -18,6 +18,10 @@ let remainingSeconds (data: QuizForAttempt) (now: DateTimeOffset) : int option =
 type Model =
     { Data: QuizForAttempt
       Answers: Map<QuestionId, StudentResponse>
+      /// Index into `Data.Questions` of the question currently shown on its
+      /// own card — questions are navigated one at a time via prev/next
+      /// arrows rather than shown all at once.
+      CurrentIndex: int
       Error: string option
       IsFinishing: bool
       RemainingSeconds: int option
@@ -30,6 +34,7 @@ type Model =
 let init (data: QuizForAttempt) : Model =
     { Data = data
       Answers = Map.empty
+      CurrentIndex = 0
       Error = None
       IsFinishing = false
       RemainingSeconds = remainingSeconds data DateTimeOffset.UtcNow
@@ -39,6 +44,7 @@ type Msg =
     | AnswerChanged of QuestionId * StudentResponse
     | AnswerSaved of QuestionId
     | AnswerSaveFailed of QuestionId * string
+    | GoToQuestion of int
     | Tick
     | FocusLost
     | FocusRegained

src/Client/Features/Quizzes/TakeQuiz/View.fs

@@ -5,7 +5,7 @@ open Domain
 open Domain.Contracts
 open Client.Features.Quizzes.TakeQuiz.Types
 
-let private questionView (answers: Map<QuestionId, StudentResponse>) dispatch (index: int) (question: QuestionView) =
+let private questionBody (answers: Map<QuestionId, StudentResponse>) dispatch (question: QuestionView) =
     let groupName = string question.Id
 
     let body =
@@ -111,18 +111,33 @@ let private questionView (answers: Map<QuestionId, StudentResponse>) dispatch (i
                     dispatch (AnswerChanged(question.Id, NumericResponse parsed)))
             ]
 
+    body
+
+let private questionCard (model: Model) dispatch (question: QuestionView) =
+    let total = List.length model.Data.Questions
+
     Html.div [
         prop.key (string question.Id)
-        prop.className "question"
+        prop.className "question-card"
         prop.children [
-            Html.span [ prop.className "question-number"; prop.text (sprintf "№ %02d" (index + 1)) ]
+            Html.span [
-            Html.div [
+                prop.className "question-number"
-                prop.className "question-body"
+                prop.text (sprintf "Вопрос %d из %d" (model.CurrentIndex + 1) total)
-                prop.children [ Html.p [ prop.className "question-text"; prop.text question.Text ]; body ]
             ]
+            Html.p [ prop.className "question-text"; prop.text question.Text ]
+            questionBody model.Answers dispatch question
         ]
     ]
 
+let private navArrow (className: string) (label: string) (enabled: bool) (onClick: unit -> unit) =
+    Html.button [
+        prop.type'.button
+        prop.className (sprintf "nav-arrow %s" className)
+        prop.disabled (not enabled)
+        prop.onClick (fun _ -> onClick ())
+        prop.text label
+    ]
+
 let private timeRemainingBadge (seconds: int) =
     Html.span [
         prop.className (if seconds <= 60 then "time-remaining low" else "time-remaining")
@@ -130,6 +145,8 @@ let private timeRemainingBadge (seconds: int) =
     ]
 
 let view (model: Model) (dispatch: Msg -> unit) =
+    let total = List.length model.Data.Questions
+
     Html.div [
         prop.className "taking-quiz-page"
         prop.children [
@@ -138,7 +155,16 @@ let view (model: Model) (dispatch: Msg -> unit) =
             | Some err -> Html.p [ prop.className "error"; prop.text err ]
             | None -> Html.none
             Html.div [
-                prop.children (model.Data.Questions |> List.mapi (questionView model.Answers dispatch))
+                prop.className "question-nav"
+                prop.children [
+                    navArrow "nav-arrow-prev" "‹" (model.CurrentIndex > 0) (fun () ->
+                        dispatch (GoToQuestion(model.CurrentIndex - 1)))
+                    match model.Data.Questions |> List.tryItem model.CurrentIndex with
+                    | Some question -> questionCard model dispatch question
+                    | None -> Html.none
+                    navArrow "nav-arrow-next" "›" (model.CurrentIndex < total - 1) (fun () ->
+                        dispatch (GoToQuestion(model.CurrentIndex + 1)))
+                ]
             ]
             Html.div [
                 prop.className "quiz-actions"

src/Client/style.css

@@ -297,28 +297,27 @@ a {
 /* ============================================================
    Taking a quiz
    ============================================================ */
-.question {
+.question-nav {
   display: flex;
-  gap: 1rem;
+  align-items: center;
-  border-top: 1px solid var(--line);
+  gap: 0.75rem;
-  padding: 1.25rem 0;
 }
 
-.question:first-of-type {
+.question-card {
-  border-top: none;
+  flex: 1;
+  min-width: 0;
+  background: var(--surface);
+  border: 1px solid var(--line);
+  border-radius: var(--radius);
+  padding: 1.5rem;
 }
 
 .question-number {
+  display: block;
   font-family: var(--font-mono);
   font-size: 0.85rem;
   color: var(--brass);
-  flex-shrink: 0;
+  margin-bottom: 0.6rem;
-  padding-top: 0.15rem;
-}
-
-.question-body {
-  flex: 1;
-  min-width: 0;
 }
 
 .question-text {
@@ -326,6 +325,23 @@ a {
   margin-bottom: 0.6rem;
 }
 
+.nav-arrow {
+  flex-shrink: 0;
+  width: 2.5rem;
+  height: 2.5rem;
+  padding: 0;
+  font-size: 1.3rem;
+  line-height: 1;
+  border-radius: 50%;
+  background: var(--surface);
+  color: var(--ink);
+  border: 1px solid var(--line);
+}
+
+.nav-arrow:hover:not(:disabled) {
+  background: var(--brass-soft);
+}
+
 .option {
   display: flex;
   align-items: center;
@@ -730,6 +746,24 @@ a {
   padding: 0.3rem 0;
 }
 
+.topic-checkbox-list {
+  display: flex;
+  flex-wrap: wrap;
+  gap: 0 1rem;
+  margin-bottom: 0.5rem;
+}
+
+.topic-picker-section {
+  border: 1px solid var(--line);
+  border-radius: var(--radius);
+  padding: 0.75rem 1rem;
+  margin-bottom: 0.75rem;
+}
+
+.topic-picker-section h4 {
+  margin: 0 0 0.5rem;
+}
+
 /* ---- Modal overlay (quiz create/edit form) ---- */
 
 .modal-backdrop {