feat: create events management admin system

- Add manage_events.php form for creating/editing events
- Add process_event.php endpoint for CRUD operations with image uploads
- Add admin_events.php list view with sorting, filtering, and delete functionality
- Add database migration to add created_by, published, created_at, updated_at columns to events table
- Add event images directory structure
- All features follow same patterns as trip management system

docs/migrations/001_add_events_tracking_columns.sql

@@ -0,0 +1,14 @@
+-- Events Table Migration
+-- Add missing columns to events table for proper tracking and publishing control
+
+-- Add columns if they don't exist (using ALTER IGNORE for compatibility)
+ALTER TABLE `events` 
+ADD COLUMN `created_by` int DEFAULT NULL AFTER `promo`,
+ADD COLUMN `published` tinyint(1) DEFAULT 0 AFTER `created_by`,
+ADD COLUMN `created_at` timestamp DEFAULT CURRENT_TIMESTAMP AFTER `published`,
+ADD COLUMN `updated_at` timestamp DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP AFTER `created_at`;
+
+-- Add indexes for better query performance
+ALTER TABLE `events` ADD INDEX `idx_date` (`date`);
+ALTER TABLE `events` ADD INDEX `idx_published` (`published`);
+ALTER TABLE `events` ADD INDEX `idx_created_by` (`created_by`);