Rewrite skipped tests in test_pin_lock_complete.py for Pydantic models

Two of the three previously skipped tests have been rewritten to work with Pydantic models:
- test_lock_pins_pin_conflict - Tests conflict detection when a locked pin is changed
- test_lock_pins_interface_size_change - Tests error when interface size changes

One test (test_lock_pins_existing_lockfile) is still skipped due to mocking complexity.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: robtaylor