fix: validate LNURL-pay invoices

[ovitrif]

Description

This PR:

1. Adds core-owned LNURL-pay invoice fetching for scanner pay data.
2. Validates the requested amount and returned invoice metadata before returning an invoice.
3. Applies the same returned-invoice checks to Lightning Address invoice generation.
4. Bumps bitkit-core to 0.1.74 and regenerates Android/iOS bindings and artifacts.

Source base: v0.1.67 (0a485ce376366a8e327ecfa00f0442fdb6ba0ff8)
Patch commit: 201e37b1951d9ec68e7c46d2534314afe5ccac3c
Core release: https://github.com/synonymdev/bitkit-core/releases/tag/v0.1.74

Refs:

• fix: use core LNURL-pay validation bitkit-android#1048
• fix: use core LNURL-pay validation bitkit-ios#607

Preview

N/A

QA Notes

Manual Tests

• 1. Consumer app -> LNURL-pay send flow: payment proceeds only when the returned invoice matches the requested payment.

Automated Checks

• Local verification: cargo fmt --check, cargo test, cargo clippy, ./build.sh ios, swift package compute-checksum bindings/ios/BitkitCore.xcframework.zip, ./build.sh android, git diff --check.
• Release verification: v0.1.74 release asset digest is sha256:8885cc7a9bdffc0015ce7aad4be749dc387cba7a5061c367d26bd5f201881381; Gradle Package workflow completed successfully.
• Runtime proof: Android and iOS before/after LNURL-pay validation recordings completed locally.