Fix helpers/config: timezone, comment leak, silent misconfig, cache perms

- Database.php: pin MySQL session time_zone to the configured named zone
  (mysql.time_zone tables now loaded on the DB) with a fixed-offset
  fallback, so NOW()/TIMESTAMP and PHP agree regardless of the DB server's
  SYSTEM tz. Best-effort, never fatals the connection.
- NotificationHelper: redact comment-body previews for internal/
  confidential tickets in sendCommentNotification and notifyWatchers so
  they are not leaked to the shared Matrix notify list (new $visibility
  param; callers wired in the API batch).
- config.php: die with a clear error if parse_ini_file fails instead of
  silently falling back to insecure defaults (empty DB pass / proxies).
- CacheHelper: create cache dir 0700 and cache files 0600 so other local
  users cannot read or poison security-relevant cached data.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

config/config.php

@@ -6,6 +6,9 @@ if (!file_exists($envFile)) {
     die('Configuration error: .env file not found. Copy .env.example to .env and configure your database settings.');
 }
 $envVars = parse_ini_file($envFile, false, INI_SCANNER_TYPED);
+if (!is_array($envVars)) {
+    die('Configuration error: .env file could not be parsed. Check for unquoted special characters (e.g. #, ;, =, or quotes) in values and wrap affected values in double quotes.');
+}
 
 // Strip quotes from values if present (parse_ini_file may include them)
 if ($envVars) {