feat(ui): one CountBadge for all counters; counters on tab corners

- CountBadge component (accent / muted, inline / corner, 99+, showZero);
  used in the nav bar, task list and list tabs, admin organizations and
  numeric badges of the mobile menu; old badge-count removed
- Counters sit on the top right corner of tabs; "Alle Aufgaben" gets one
  (desktop tab and mobile menu)
- Open/done task counters include tasks in shared lists, matching what
  "Alle Aufgaben" shows (nav counter was too low)
- Theme template derives --accent-dim/--accent-border from the accent
- Docs: ui-patterns counters section

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/storage/sqlite.go

@@ -4080,8 +4080,10 @@ func (s *Store) ValidateAPIKeyAndGetUser(rawKey string) (*domain.User, error) {
 func (s *Store) GetDashboardStats(userID string) (*domain.DashboardStats, error) {
 	st := &domain.DashboardStats{}
 	_ = s.db.QueryRow(`SELECT COUNT(*) FROM thoughts WHERE user_id = ? AND status = 'inbox'`, userID).Scan(&st.InboxCount)
-	_ = s.db.QueryRow(`SELECT COUNT(*) FROM thoughts WHERE user_id = ? AND (status = 'kept' OR (status = 'converted' AND converted_type = 'task')) AND is_completed = 0`, userID).Scan(&st.TasksOpenCount)
-	_ = s.db.QueryRow(`SELECT COUNT(*) FROM thoughts WHERE user_id = ? AND (status = 'kept' OR (status = 'converted' AND converted_type = 'task')) AND is_completed = 1`, userID).Scan(&st.TasksDoneCount)
+	// Same tasks as GetTasks without a list ("Alle Aufgaben"): own ones plus those in shared task lists
+	taskScope := `(user_id = ? OR task_list_id IN (` + s.accessibleTaskListIDsQuery() + `)) AND (status = 'kept' OR (status = 'converted' AND converted_type = 'task'))`
+	_ = s.db.QueryRow(`SELECT COUNT(*) FROM thoughts WHERE `+taskScope+` AND is_completed = 0`, userID, userID, userID, userID).Scan(&st.TasksOpenCount)
+	_ = s.db.QueryRow(`SELECT COUNT(*) FROM thoughts WHERE `+taskScope+` AND is_completed = 1`, userID, userID, userID, userID).Scan(&st.TasksDoneCount)
 	_ = s.db.QueryRow(`SELECT COUNT(*) FROM documents WHERE user_id = ? AND is_archived = 0`, userID).Scan(&st.DocsCount)
 	_ = s.db.QueryRow(`SELECT COUNT(*) FROM thoughts WHERE user_id = ? AND status = 'discarded'`, userID).Scan(&st.DiscardedCount)
 	_ = s.db.QueryRow(`