Add V2 data collection camera mount and organize V1 assets

[Yang-Ci]

Adds the V2 data collection camera mount assembly with an aluminum extrusion support body and a 3D-printed camera bracket. Moves the original four V1 mounts and four adapters into hardware/camera-mounts/data-collection-camera-mounts/V1/, making the two construction versions clear in the English and Chinese catalogs.

The V2 STEP file uses the English filename data-collection-camera-mount-v2.stp and includes a preview rendered directly from its assembly geometry. All CAD bytes are preserved. Source attribution records Yang-Ci/Camera-Mounts at a859dc8; existing B601-RS/B601-DM sharing notes remain in the catalog. The preview tool discovers files recursively and supports rendering a selected file.

Validation:

• Verified byte-for-byte preservation of all eight V1 CAD files and the supplied V2 STEP file.
• Checked local links and all 14 model entries/previews in both catalogs.
• Regenerated the V2 assembly preview using the documented command.
• README translation checker and its nine tests pass; git diff --check passes.

Also wraps six existing Chinese/Japanese README email addresses in explicit mailto: links. The previous documentation CI interpreted those bare addresses as missing local files; the names and addresses are unchanged.