feat: Anki export button - download all 190 cards as TSV file from flashcards page

edu/api/decks.php

@@ -18,6 +18,38 @@ if (get_method() === 'GET' && empty($segments[1])) {
     json_ok(['decks' => $stmt->fetchAll()]);
 }
 
+// GET /api/decks/export-anki — download all cards as Anki TSV
+if (get_method() === 'GET' && ($segments[1] ?? '') === 'export-anki') {
+    $stmt = $pdo->query("
+        SELECT d.name AS deck_name, c.question, c.answer, c.level
+        FROM cards c JOIN decks d ON d.id = c.deck_id
+        ORDER BY d.sort_order, d.name, c.sort_order
+    ");
+    $cards = $stmt->fetchAll();
+
+    header('Content-Type: text/tab-separated-values; charset=utf-8');
+    header('Content-Disposition: attachment; filename="sol2_training_anki_' . date('Y-m-d') . '.txt"');
+    header('Cache-Control: no-cache');
+
+    // Clean markdown formatting for Anki: backticks -> <code>, ** -> <b>
+    function anki_format($text) {
+        $t = $text;
+        $t = preg_replace('/```(\w*)\n(.*?)```/s', '<pre><code>$2</code></pre>', $t);
+        $t = str_replace('`', '', $t);
+        $t = preg_replace('/\*\*(.+?)\*\*/', '<b>$1</b>', $t);
+        $t = str_replace("\n", '<br>', $t);
+        $t = str_replace("\t", ' ', $t);
+        return $t;
+    }
+
+    foreach ($cards as $c) {
+        $q = anki_format($c['question']);
+        $a = anki_format($c['answer']);
+        echo $q . "\t" . $a . "\t" . 'Sol2-Training::' . $c['deck_name'] . "\t" . $c['level'] . "\n";
+    }
+    exit;
+}
+
 // GET /api/decks/{slug}
 if (get_method() === 'GET' && !empty($segments[1])) {
     $stmt = $pdo->prepare("SELECT * FROM decks WHERE slug = :s");