v0.3.0

What's new

• Payment watch: payments.watch() SSE stream for real-time payment events (settled/failed) — both sync and async
• Unauthenticated invoice creation: invoices.create_for_wallet() and invoices.create_for_address() — no API key required
• LNURL support: payments.create() now accepts LNURL targets alongside Lightning addresses and BOLT11 invoices
• New types: PaymentEvent, AddressInvoiceResponse