fix(databases): keep the server password of existing Redis databases

v4.3.23 started Redis with the stored REDIS_PASSWORD value as it is and
unquoted, and the connection URLs used the same value. 4.4.0 resolved a
shared variable reference for the start command only, so after the first
restart the server password changed and no longer matched the URLs.

- Add legacy_password_quoting to standalone_redis; existing databases
  keep the v4.3.23 server password
- New databases resolve REDIS_PASSWORD (local, shared or remote secret)
  and quote it in the start command
- Connection URLs use the same password as the server
- Hide the flag in the API, as for KeyDB and Dragonfly

database/migrations/2026_10_05_204113_add_legacy_password_quoting_to_standalone_redis.php

@@ -0,0 +1,30 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\DB;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    /**
+     * Until v4.3.23, the Redis start command and connection URLs used the stored REDIS_PASSWORD value
+     * as it is (a shared variable reference stayed text) and the command did not quote it. Existing
+     * databases keep that server password; databases created later resolve and quote it.
+     */
+    public function up(): void
+    {
+        Schema::table('standalone_redis', function (Blueprint $table) {
+            $table->boolean('legacy_password_quoting')->default(false);
+        });
+
+        DB::table('standalone_redis')->update(['legacy_password_quoting' => true]);
+    }
+
+    public function down(): void
+    {
+        Schema::table('standalone_redis', function (Blueprint $table) {
+            $table->dropColumn('legacy_password_quoting');
+        });
+    }
+};