feat: Implement WebhooksService and wire sweep event notifications - #450

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@v4, actions/setup-node@v4. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

Unsafe argument of type error typed assigned to a parameter of type `string | symbol | Function | Type<AccountsService>`

Unsafe argument of type error typed assigned to a parameter of type `string | symbol | Function | Type<StellarService>`

Unsafe argument of type `any` assigned to a parameter of type `Reflector`