Release v1.0.0: migrate Explorer to bitcoinjs-lib v7 and descriptors v3

[landabaso]

This PR marks the @bitcoinerlab/explorer 1.0.0 release and aligns the package with the current bitcoinerlab stack. The goal is to keep Explorer in sync with the same bjs7 direction adopted in descriptors, while cleaning up older internals that were still tied to Buffer-based handling.

The dependency upgrade is the core of this change: Explorer now targets bitcoinjs-lib@7 and @bitcoinerlab/descriptors@3. Alongside that, the codebase was updated to follow Uint8Array-first patterns, using uint8array-tools for hex conversions so Buffer is no longer used in TypeScript sources. Electrum network resolution was also hardened by switching from object-identity checks to value-based network matching, which makes cloned network objects behave as expected when picking default servers.

The integration tests were migrated to the new descriptors API to reflect the same runtime contract we now depend on.

This is a breaking release by design. While Explorer’s high-level fetch/push interface remains stable, projects that share transaction-building/signing flows with Explorer or pin older versions of the Bitcoin JS stack should expect migration work. In particular, consumers moving from the previous stack should account for descriptors v3 API changes and bitcoinjs-lib@7 conventions around bigint values and Uint8Array handling.