Add Turnstile protection and harden export workflow

gemeinden.php

@@ -1,4 +1,8 @@
 
 <?php
-echo "communityCsvData = `". communityCSV($username, $password) ."`;";
-?>
+$communityCsv = app_cached_string(
+    'communities',
+    app_env_int('REFERENCE_CACHE_SECONDS', 86400, 300, 604800),
+    static fn(): string => communityCSV((string)$username, (string)$password)
+);
+echo 'communityCsvData = ' . json_encode($communityCsv, JSON_HEX_TAG | JSON_HEX_AMP | JSON_HEX_APOS | JSON_HEX_QUOT) . ';';