feat: add FEN block support and related assets

Introduced a new FEN block feature, including a PHP snippet to render FEN diagrams, a new CSS file for chessboard styling, font integration, and blueprint updates. Adjusted asset paths and file references for consistency.

site/templates/blockpage.php

@@ -0,0 +1,32 @@
+<?php
+
+// FEN in Array umwandeln
+function fenToBoard($fen) {
+    $rows  = explode('/', explode(' ', $fen)[0]);
+    $board = [];
+    foreach ($rows as $row) {
+        $boardRow = [];
+        $chars    = str_split($row);
+        foreach ($chars as $char) {
+            if (is_numeric($char)) {
+                for ($i = 0; $i < intval($char); $i++) {
+                    $boardRow[] = '';
+                }
+            } else {
+                $boardRow[] = $char;
+            }
+        }
+        $board[] = $boardRow;
+    }
+
+    return $board;
+} ?>
+
+
+<?php
+snippet('layout', slots: true) ?>
+
+<?= $page->blocks()->toBlocks() ?>
+
+<?php
+endsnippet() ?>