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>

migrations/010_add_bulk_operations.sql

@@ -0,0 +1,19 @@
+-- Migration 010: Add bulk operations tracking
+-- Creates bulk_operations table for admin bulk actions
+
+CREATE TABLE bulk_operations (
+    operation_id INT AUTO_INCREMENT PRIMARY KEY,
+    operation_type VARCHAR(50) NOT NULL,
+    ticket_ids TEXT NOT NULL, -- Comma-separated
+    performed_by INT NOT NULL,
+    parameters JSON,
+    status VARCHAR(20) DEFAULT 'pending',
+    total_tickets INT,
+    processed_tickets INT DEFAULT 0,
+    failed_tickets INT DEFAULT 0,
+    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+    completed_at TIMESTAMP NULL,
+    FOREIGN KEY (performed_by) REFERENCES users(user_id),
+    INDEX idx_performed_by (performed_by),
+    INDEX idx_created_at (created_at)
+);