chore: scaffold yunke-server

Create pyproject.toml (FastAPI + SQLAlchemy + Playwright + APScheduler +
Redis + cryptography stack), .env.example, app/__init__.py and a
pydantic-settings Settings singleton (get_settings), and a root
.gitignore covering Python, Node, env, IDE and the local media dir.

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

yunke-server/.env.example

@@ -0,0 +1,9 @@
+YUNKE_BASE_URL=https://crm2.yunkecn.com
+YUNKE_USERNAME=
+YUNKE_PASSWORD=
+DB_URL=mysql+asyncmy://user:pass@localhost:3306/yunke
+REDIS_URL=redis://localhost:6379/0
+MEDIA_DIR=./media
+# Fernet key (e.g. from cryptography.fernet.Fernet.generate_key()) used to encrypt
+# stored credentials. Required for real runs; left blank for tests.
+ENCRYPTION_KEY=