fix: Session auth, sidebar toggle, and dependencies table

- Change session.cookie_samesite from Strict to Lax for Authelia compatibility
- Redesign sidebar toggle with separate collapse/expand buttons
- Add script to create missing ticket_dependencies table
- Add .env.example template
- Add check for missing .env with helpful error message

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

config/config.php

@@ -1,6 +1,9 @@
 <?php
 // Load environment variables
 $envFile = __DIR__ . '/../.env';
+if (!file_exists($envFile)) {
+    die('Configuration error: .env file not found. Copy .env.example to .env and configure your database settings.');
+}
 $envVars = parse_ini_file($envFile, false, INI_SCANNER_TYPED);
 
 // Strip quotes from values if present (parse_ini_file may include them)