feat: implement 8 features across full stack

- Leaderboard: rank-based percentile tiers (champion/gold/silver/bronze),
    deterministic tie-breaking (xp DESC, user_id ASC)
  - Mentor chat: md: breakpoints, safe-area-inset-bottom padding
  - Learning progress: server-side progressPct, curriculum expansion safety
  - Physical orders: hard-disabled with 410 Gone
  - Certificate approval: pending/issued flow, admin issue/revoke endpoints,
    certificate_requires_approval setting (migration 0031)
  - Draft/publish: is_published on lessons and chapters, admin publish UI
    (migration 0030)
  - Video panel: static thumbnails (no preload), client-side pagination
  - Rich editor: TipTap + tiptap-markdown for lesson descriptions,
    marked + DOMPurify for SafeMarkdown rendering

backend/internal/api/tree.go

@@ -57,6 +57,23 @@ func (s *Server) handleTree(w http.ResponseWriter, r *http.Request) {
 		}
 	}
 
+	// Compute progress aggregates using only active+published lessons as the denominator so
+	// that frontend and backend always agree on the percentage.
+	totalActive, completedActive := 0, 0
+	for _, l := range lessons {
+		if !l.IsActive || !l.IsPublished {
+			continue
+		}
+		totalActive++
+		if p, ok := progress[l.ID]; ok && p.PassedQuiz {
+			completedActive++
+		}
+	}
+	var progressPct float64
+	if totalActive > 0 {
+		progressPct = float64(completedActive) / float64(totalActive) * 100
+	}
+
 	out := make([]chapterView, 0, len(chapters))
 	for _, ch := range chapters {
 		cv := chapterView{Chapter: ch, Lessons: []lessonView{}}
@@ -84,7 +101,10 @@ func (s *Server) handleTree(w http.ResponseWriter, r *http.Request) {
 	}
 
 	writeJSON(w, http.StatusOK, map[string]any{
-		"chapters": out,
+		"chapters":        out,
+		"totalLessons":    totalActive,
+		"completedLessons": completedActive,
+		"progressPct":     progressPct,
 		"me": map[string]any{
 			"xp":       u.XP,
 			"streak":   u.StreakCurrent,
@@ -244,7 +264,7 @@ func (s *Server) allowLessonAccess(w http.ResponseWriter, r *http.Request, lesso
 		writeErrCode(w, http.StatusLocked, CodeLocked, service.ErrLocked.Error())
 		return false
 	}
-	if !lesson.IsActive && !u.Role.IsStaff() {
+	if (!lesson.IsActive || !lesson.IsPublished) && !u.Role.IsStaff() {
 		writeErrCode(w, http.StatusNotFound, CodeNotFound, "درس پیدا نشد")
 		return false
 	}