fix: make PgBouncer prepared statement disabling configurable

Use PDO::PGSQL_ATTR_DISABLE_PREPARES with DB_DISABLE_PREPARES env variable
to prevent "cached plan must not change result type" errors during rolling
deployments with PgBouncer. Defaults to false for normal operation.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

config/database.php

@@ -49,7 +49,7 @@
             'search_path' => 'public',
             'sslmode' => 'prefer',
             'options' => [
-                PDO::ATTR_EMULATE_PREPARES => true,
+                PDO::PGSQL_ATTR_DISABLE_PREPARES => env('DB_DISABLE_PREPARES', false),
             ],
         ],