Add Activity Timeline feature and database migrations

- Add Activity Timeline tab to ticket view showing chronological history
- Create getTicketTimeline() method in AuditLogModel
- Update TicketController to load timeline data
- Add timeline UI with helper functions for formatting events
- Add comprehensive timeline CSS with dark mode support
- Create migrations 007-010 for upcoming features:
  - 007: Ticket assignment functionality
  - 008: Status workflow transitions
  - 009: Ticket templates
  - 010: Bulk operations tracking

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

models/AuditLogModel.php

@@ -289,4 +289,36 @@ class AuditLogModel {
     public function logTicketView($userId, $ticketId) {
         return $this->log($userId, 'view', 'ticket', $ticketId);
     }
+
+    /**
+     * Get formatted timeline for a specific ticket
+     * Includes all ticket updates and comments
+     *
+     * @param string $ticketId Ticket ID
+     * @return array Timeline events
+     */
+    public function getTicketTimeline($ticketId) {
+        $stmt = $this->conn->prepare(
+            "SELECT al.*, u.username, u.display_name
+             FROM audit_log al
+             LEFT JOIN users u ON al.user_id = u.user_id
+             WHERE (al.entity_type = 'ticket' AND al.entity_id = ?)
+                OR (al.entity_type = 'comment' AND JSON_EXTRACT(al.details, '$.ticket_id') = ?)
+             ORDER BY al.created_at DESC"
+        );
+        $stmt->bind_param("ss", $ticketId, $ticketId);
+        $stmt->execute();
+        $result = $stmt->get_result();
+
+        $timeline = [];
+        while ($row = $result->fetch_assoc()) {
+            if ($row['details']) {
+                $row['details'] = json_decode($row['details'], true);
+            }
+            $timeline[] = $row;
+        }
+
+        $stmt->close();
+        return $timeline;
+    }
 }