Add JWT authorization + Fixes

[PJColombo]

It adds the following:

• Add JWT auth to blobscan client requests and implement a token refreshing mechanism.
• Fix the problem about blob entities matching an incorrect tx.
• Include the following code refactoring:
  • Remove unused general types
  • Move entity types (block, tx, and blob) to their respective client package.
  • Implement entity conversion logic through the TryForm and Form traits.
  • Abstract utility mappings creation logic into their own functions.
  • Rename API components to "client" for clarity.
  • Simplify client instantiation logic.
  • Move context.rs and env.rs out of /utils folder to improve code discoverability.