feat: PHP API foundation - router, config, helpers, SM-2 algorithm

edu/api/index.php

@@ -0,0 +1,42 @@
+<?php
+require_once __DIR__ . '/config.php';
+require_once __DIR__ . '/helpers.php';
+
+// Parse: /api/decks/omnis-commands -> ['decks', 'omnis-commands']
+$request_uri = $_SERVER['REQUEST_URI'];
+$path = parse_url($request_uri, PHP_URL_PATH);
+$path = preg_replace('#^/api/?#', '', $path);
+$path = trim($path, '/');
+$segments = $path ? explode('/', $path) : [];
+$resource = $segments[0] ?? '';
+
+switch ($resource) {
+    case 'login':
+    case 'logout':
+    case 'me':
+        require __DIR__ . '/auth.php';
+        break;
+    case 'decks':
+        require __DIR__ . '/decks.php';
+        break;
+    case 'cards':
+        require __DIR__ . '/cards.php';
+        break;
+    case 'tutorials':
+        require __DIR__ . '/tutorials.php';
+        break;
+    case 'quiz':
+        require __DIR__ . '/quiz.php';
+        break;
+    case 'cheatsheets':
+        require __DIR__ . '/cheatsheets.php';
+        break;
+    case 'dashboard':
+        require __DIR__ . '/dashboard.php';
+        break;
+    case 'admin':
+        require __DIR__ . '/admin.php';
+        break;
+    default:
+        json_error('Unbekannter Endpunkt', 404);
+}