Fix MockRoutingService Logic Bugs

[MRiabov]

Fixed critical bugs in MockRoutingService:

1. Distance Calculation: Previously, the service calculated distance from the employee's default start location for every job in the sequence. It now correctly updates the employee's location after each assignment, calculating the distance from the previous job to the current job.
2. Travel Time Calculation: Corrected unit mismatch where km were treated as meters or incorrect formula was used. Now uses _haversine (km) and assumes 30km/h speed.
3. Availability Windows: Implemented _check_availability to respect CustomerAvailability windows. Jobs are now scheduled within open windows, waiting if early, or skipped if they don't fit.

Added tests/test_mock_routing_regression.py to verify these fixes and prevent regression.

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PR created automatically by Jules for task 9597031689121396872 started by @MRiabov

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