feat: Add admin navigation, fix modals, clickable stats, update docs

- Add admin dropdown menu in dashboard header with links to all admin pages
- Fix template modal: larger size (800px), responsive grid, type/priority dropdowns
- Fix recurring tickets modal: add Type and Assign To fields, larger size
- Make dashboard stat cards clickable for quick filtering
- Fix user-activity query (remove is_active requirement)
- Add table existence check in ticket_dependencies API
- Fix table overflow on dashboard
- Update Claude.md and README.md with current project status
- Remove migrations directory (all migrations completed)

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

api/ticket_dependencies.php

@@ -1,18 +1,34 @@
 <?php
 /**
  * Ticket Dependencies API
- *
- * GET: Get dependencies for a ticket
- * POST: Add a new dependency
- * DELETE: Remove a dependency
  */
 
-// Capture ALL errors for debugging
+// Immediately set JSON header and start output buffering
+ob_start();
+header('Content-Type: application/json');
+
+// Register shutdown function to catch fatal errors
+register_shutdown_function(function() {
+    $error = error_get_last();
+    if ($error && in_array($error['type'], [E_ERROR, E_PARSE, E_CORE_ERROR, E_COMPILE_ERROR])) {
+        ob_end_clean();
+        http_response_code(500);
+        header('Content-Type: application/json');
+        echo json_encode([
+            'success' => false,
+            'error' => 'Fatal: ' . $error['message'],
+            'file' => basename($error['file']),
+            'line' => $error['line']
+        ]);
+    }
+});
+
 ini_set('display_errors', 0);
 error_reporting(E_ALL);
 
-// Custom error handler to return JSON errors
+// Custom error handler
 set_error_handler(function($errno, $errstr, $errfile, $errline) {
+    ob_end_clean();
     http_response_code(500);
     header('Content-Type: application/json');
     echo json_encode([
@@ -26,6 +42,7 @@ set_error_handler(function($errno, $errstr, $errfile, $errline) {
 
 // Custom exception handler
 set_exception_handler(function($e) {
+    ob_end_clean();
     http_response_code(500);
     header('Content-Type: application/json');
     echo json_encode([
@@ -81,6 +98,12 @@ if ($conn->connect_error) {
     ResponseHelper::serverError('Database connection failed');
 }
 
+// Check if ticket_dependencies table exists
+$tableCheck = $conn->query("SHOW TABLES LIKE 'ticket_dependencies'");
+if ($tableCheck->num_rows === 0) {
+    ResponseHelper::serverError('Ticket dependencies feature not available. The ticket_dependencies table does not exist. Please run the migration.');
+}
+
 try {
     $dependencyModel = new DependencyModel($conn);
     $auditLog = new AuditLogModel($conn);