fix: decode 16UC depth images as uint16

[MiaoDX]

Summary

• fix the vendored Python cv_bridge type map for 16UC1..4 encodings
• add a focused regression test that checks 16UC1 stays uint16 and preserves depth values

Why

The previous mapping decoded 16UC1 as uint8, which corrupts millimeter depth images and breaks downstream point cloud visualization.

Verification

• python -m pytest decoupled_wbc/tests/control/utils/test_cv_bridge.py -q

[MiaoDX]

@ZhengyiLuo PTAL.