fix: decouple DEXExtension execution and port Curve25519 weak key safeguards

[D-H-O-R-A]

This PR resolves dynamic classloader linkage issues when running the DEX extension within the newly updated JVM node and ports critical cryptographic safety checks.

Key changes:

1. Thread Pool Decoupling in DEXExtension:

   • Removed direct dependency on the node's context.actorSystem dispatcher, which caused classloader linkage errors due to Akka-to-Pekko/Scala 3 transition.
   • Implemented an internally managed, isolated JVM thread pool (ScheduledExecutorService wrapped inside a Monix Scheduler).
   • Added structured lifecycle hooks to gracefully shut down the thread pool during extension shutdown to avoid thread leaks.

2. Curve25519 Low-Order Weak Key Protection:

   • Ported the isWeakPublicKey and BlacklistedKeys safety validation from the node into the Matcher domain core (package.scala in waves-integration).
   • Overrode signature verification (verify) to reject weak public keys by default, blocking potential signature forgery and spoofing attacks at the REST API entrypoint.
   • Preserved compatibility by allowing optional bypass (checkWeakPk = false) for legacy internal validation paths.

3. Validation and Environment:

   • Upgraded SBT version to 1.12.11 to ensure perfect building and task execution compatibility under OpenJDK 17.
   • Added comprehensive unit tests in CryptoSpec.scala covering weak key rejection, standard key acceptance, and bypass parameters.

Developer Contact:

• Email: diegoantunes2301@gmail.com
• WhatsApp: +5511974289097