U-turn routing was not correctly utilizing designated turning facilities (turning_circle, turning_loop, mini_roundabout) attached as branches off a main road. The router would fall back to dead-end u-turns on the main road instead.

Changes

• features/car/turning_circle_uturn.feature: Existing test expectations for scenarios 3 (mini_roundabout branch) and 4 (multiple turning facilities) reflect the correct expected behavior — route should detour via the turning facility branch rather than reversing at the far end of the main road
• Implementation fix needed: The has_turning_facility flag in edge_based_graph_factory.cpp and the corresponding isTurnAllowed path need to ensure that u-turns at mini_roundabout nodes and in multi-branch topologies are correctly identified and cost-advantaged over dead-end reversals
• New test: Interior turning circle scenario to be added — a turning circle that is an intermediate node in the graph rather than a dead-end, verifying the facility is used regardless of topology position

Failing scenarios

# Scenario 3 - mini_roundabout not used as turning facility
| a,a | abcd,be,abcd | depart,turn right,turn right,arrive |
# actual: abcd,abcd | depart,arrive  (routes via dead end d, not branch e)

# Scenario 4 - multiple facilities, closest not chosen  
| a,a | abcde,bf,abcde | depart,turn right,turn right,arrive |
# actual: abcde,abcde | depart,arrive

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