Added dummy TableDetection and web app toggling of table detection

[amalnanavati]

Description

This PR, joint with ada_feeding#171, implements automated table detection into the robot-assisted feedingg system. Specifically, this PR extends the web app to toggle table detection on when the app switches to bite selection, and off when the app moves away from bite selection. Further, this PR implements a dummy TableDetection node (to continue the invariant that all real ROS interfaces have dummy variants, so the app can be tested in isolation).

Testing

Dummy:

• [x] Launch code: python3 src/ada_feeding/start.py --sim dummy
• [x] Echo the table detection topic: ros2 topic echo /table_detection. Verify that nothing is being published on that topic.
• [x] Click “Start Feeding” in the web app. Once the app switches to Bite Selection, verify that table detection poses do start getting published.
• [x] Click “Skip Acquisition.” Verify that table detection poses stop being published.

Mock:

• [x] Launch code: python3 src/ada_feeding/start.py --sim mock
• [x] Click “Start Feeding” in the web app. Once the app switches to Bite Selection, verify that the table moves.

Real: see ada_feeding#171 for test cases and results.

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