Add start-test.bat for an isolated Docker test stand

Runs a separate compose project (pgames-test) on port 8090 with its own
.env.test and data-test/, starts Docker Desktop if needed and generates a
sample game to upload. env_file in compose is now overridable via ENV_FILE.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.gitignore

@@ -6,3 +6,5 @@ __pycache__/
 .pytest_cache/
 *.pyc
 sample.zip
+.env.test
+data-test/