Feat/abstractions

[d4rp4t]

this pr introduces abstraction layer on top of the library

Summary by CodeRabbit

• New Features
  • Fluent wallet APIs for mint/melt/swap/restore (Bolt11 & Bolt12), HTLC & P2PK locking, deterministic output derivation, and a full WebSocket subscription/service for real‑time quote and proof updates.
• Improvements
  • Stronger signing/verification, improved proof selection, per‑keyset counter with fetch‑and‑increment, richer mint capability detection, and refined fee handling.
• Tests
  • Large new integration suite and many unit tests covering wallet and WebSocket flows.
• Chores
  • CI reorganized: tests run in a dedicated workflow job.