Paper preview in ZenithPrep style: stat cards, subject sections

shared() now renders: stat cards (questions, duration, max marks,
+4/-1), per-subject sections with q-ranges and chapter lists, a
'take this paper' card with the save-and-next explainer and privacy
note, then the full question list. New .kv/.grid2/.subj-sec/.ch-list
CSS with mobile single-column fallback.

src/views.rs

@@ -1216,6 +1216,39 @@ pub fn dashboard(ctx: &Ctx, user: &str, tests: &[TestRow], weak: &[(Bucket, Stri
 }
 
 pub fn shared(ctx: &Ctx, title: &str, duration: i64, questions: &[Question], paper_id: &str, token: &str, signed: bool) -> String {
+    use std::collections::BTreeMap;
+    // Group questions by subject, preserving first-seen order.
+    let mut order: Vec<String> = Vec::new();
+    let mut by_subj: BTreeMap<String, Vec<(usize, &Question)>> = BTreeMap::new();
+    for (i, q) in questions.iter().enumerate() {
+        if !by_subj.contains_key(&q.subject) {
+            order.push(q.subject.clone());
+        }
+        by_subj.entry(q.subject.clone()).or_default().push((i, q));
+    }
+    let n = questions.len();
+    let max_marks = n as i64 * 4;
+    // Subject sections with chapter lists.
+    let mut sections = String::new();
+    for subj in &order {
+        let qs = &by_subj[subj];
+        let start = qs.first().map(|(i, _)| i + 1).unwrap_or(1);
+        let end = qs.last().map(|(i, _)| i + 1).unwrap_or(n);
+        let mut chapters: Vec<String> = Vec::new();
+        for (_, q) in qs {
+            if !chapters.iter().any(|c| c == &q.chapter) {
+                chapters.push(q.chapter.clone());
+            }
+        }
+        let ch_list: String = chapters.iter().map(|c| format!("<li>{}</li>", esc(c))).collect();
+        sections.push_str(&format!(
+            r#"<div class="card subj-sec"><h3>{subj} <span class="dim">q{start}–q{end}</span></h3><ul class="ch-list">{chs}</ul></div>"#,
+            subj = esc(subj),
+            start = start,
+            end = end,
+            chs = ch_list
+        ));
+    }
     let qs: String = questions
         .iter()
         .enumerate()
@@ -1253,12 +1286,23 @@ pub fn shared(ctx: &Ctx, title: &str, duration: i64, questions: &[Question], pap
         )
     };
     let body = format!(
-        r#"<h1>{title}</h1><p class="meta">{count} questions · {dur} minutes · no answers or scores on this page.</p>{cta}<p><button class="btn" type="button" onclick="window.print()">print / PDF</button></p><div style="margin-top:16px">{qs}</div>"#,
+        r#"<h1>Practice paper</h1><p class="meta">{title} · JEE Main pattern · no answers or scores on this page.</p>
+<div class="kv">
+  <div class="card"><span class="dim">questions</span><b>{count}</b></div>
+  <div class="card"><span class="dim">duration</span><b>{dur} min</b></div>
+  <div class="card"><span class="dim">maximum marks</span><b>{max}</b></div>
+  <div class="card"><span class="dim">marking</span><b>+4 / −1</b></div>
+</div>
+<div class="grid2"><div>{sections}</div><div class="card"><h3>take this paper</h3><p class="meta">The online test works like the real exam: answers count only after save &amp; next.</p>{cta}<p><button class="btn" type="button" onclick="window.print()">print / PDF</button></p><p class="meta">Only the question paper is shared. Your answers and score stay private.</p></div></div>
+<h2>every question</h2>
+<div style="margin-top:12px">{qs}</div>"#,
         title = esc(title),
         count = questions.len(),
         dur = duration,
-        qs = qs,
-        cta = cta
+        max = max_marks,
+        sections = sections,
+        cta = cta,
+        qs = qs
     );
     shell(ctx, None, title, body)
 }

static/style.css

@@ -2229,3 +2229,44 @@ img.brand-logo {
   vertical-align: middle;
   filter: drop-shadow(0 0 6px rgba(59, 130, 246, 0.3));
 }
+
+/* ===== paper preview: stat cards + subject sections ===== */
+.kv {
+  display: grid;
+  grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
+  gap: 12px;
+  margin: 16px 0;
+}
+.kv .card {
+  text-align: center;
+  padding: 16px 12px;
+}
+.kv .card b {
+  display: block;
+  font-size: 1.5rem;
+  margin-top: 4px;
+}
+.grid2 {
+  display: grid;
+  grid-template-columns: 1fr 320px;
+  gap: 16px;
+  margin: 16px 0;
+}
+@media (max-width: 760px) {
+  .grid2 { grid-template-columns: 1fr; }
+}
+.subj-sec { margin-bottom: 12px; }
+.subj-sec h3 { margin-bottom: 8px; }
+.ch-list {
+  list-style: none;
+  margin: 0;
+  padding: 0;
+  columns: 2;
+  font-size: 0.85rem;
+  color: var(--text-main);
+}
+.ch-list li { margin-bottom: 4px; }
+.ch-list li::before { content: "• "; color: var(--text-dim); }
+@media (max-width: 560px) {
+  .ch-list { columns: 1; }
+}