feat: trend dots on stat cards, team workload panel, stat model improvement

- Dashboard stat cards now show lt-dot trend indicators (up/warn/idle) based on
  created_today vs closed_today flow — no extra DB query needed
- Add collapsible Team Workload panel showing assignee open ticket counts with
  progress bars (green/cyan/red by load), avatar, and name
- StatsModel.getTicketsByAssignee() now returns proper objects with user_id,
  display_name, open_count (was name-keyed flat array); limit raised to 8

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

models/StatsModel.php

@@ -25,16 +25,17 @@ class StatsModel {
     /**
      * Get tickets by assignee (top 5)
      */
-    public function getTicketsByAssignee(int $limit = 5): array {
+    public function getTicketsByAssignee(int $limit = 8): array {
         $sql = "SELECT
+                    u.user_id,
                     u.display_name,
                     u.username,
-                    COUNT(t.ticket_id) as ticket_count
+                    COUNT(t.ticket_id) as open_count
                 FROM tickets t
                 LEFT JOIN users u ON t.assigned_to = u.user_id
-                WHERE t.status != 'Closed'
+                WHERE t.status != 'Closed' AND t.assigned_to IS NOT NULL
                 GROUP BY t.assigned_to
-                ORDER BY ticket_count DESC
+                ORDER BY open_count DESC
                 LIMIT ?";
         $stmt = $this->conn->prepare($sql);
         $stmt->bind_param('i', $limit);
@@ -42,8 +43,12 @@ class StatsModel {
         $result = $stmt->get_result();
         $data = [];
         while ($row = $result->fetch_assoc()) {
-            $name = $row['display_name'] ?: $row['username'];
-            $data[$name] = (int)$row['ticket_count'];
+            $data[] = [
+                'user_id'      => (int)$row['user_id'],
+                'display_name' => $row['display_name'] ?: $row['username'],
+                'username'     => $row['username'],
+                'open_count'   => (int)$row['open_count'],
+            ];
         }
         $stmt->close();
         return $data;