feat: add synthetic actuation feedback node

[lblommesteyn]

Problem
Control waits for /ap1/actuation/speed before publishing steering, motor power, and brake commands. During bag-only or software-only smoke tests, there is no hardware/sim actuation feedback publisher, so the control loop stalls even if planning publishes target_path and speed_profile.

Changes

• Add synthetic_actuation_feedback_node.
• Publish FloatStamped speed on /ap1/actuation/speed.
• Publish FloatStamped turn angle on /ap1/actuation/turn_angle.
• Add parameters for speed_mps, turn_angle_rad, and publish_rate_hz.
• Install the executable from ap1_control.

Test plan

• colcon build --symlink-install --packages-select ap1_control --cmake-args -DCMAKE_BUILD_TYPE=Release
• git diff --check

Notes
This is for integration/smoke testing only. It does not replace real hardware or sim feedback.

[lblommesteyn]

Verified locally in the software smoke-test stack: with synthetic perception + synthetic odometry + this node, /ap1/control/motor_power and /ap1/control/turn_angle both publish.