Fix migration runner: strip -- comments before splitting statements

A semicolon inside a SQL comment (as in 001 and 003) cut statements in half and
made those migrations fail on a fresh database.

migrations/migrate.php

@@ -141,9 +141,12 @@ foreach ($pending as $file) {
     // DDL.
     try {
         // Split by semicolon but respect statements properly
-        // Note: This doesn't handle semicolons in strings, but our migrations are simple
+        // Note: This doesn't handle semicolons in strings, but our migrations are simple.
+        // Full-line "--" comments are stripped first so a ";" inside a comment
+        // can't cut a statement in half.
+        $sqlNoComments = preg_replace('/^\s*--.*$/m', '', $sql);
         $statements = array_values(array_filter(
-            array_map('trim', explode(';', $sql)),
+            array_map('trim', explode(';', $sqlNoComments)),
             function($stmt) {
                 // Remove comments and check if there's actual SQL
                 $cleaned = preg_replace('/--.*$/m', '', $stmt);