fixture: configure Clarinet Devnet local testing integration

[devmocrea]

Description

Add devnet configuration files to apps/stacks to support running complete end-to-end integration tests locally using Clarinet Devnet.

Technical Specification

• Create a standard Clarinet configuration mapping devnet credentials.
• Add mock bootstrap addresses to emulate Leather wallet connections during local runs.

Acceptance Criteria

• Devnet compiles and runs integration assertions without errors.