Add G703 support, product art, and non-lightstrip RGB zones

[dwei30]

Summary

• List G703 (wired, PID 0xc087) as supported: HID++ direct, legacy DPI 0x2201, onboard format 3 writable.
• Add top-down G703 HERO gallery art (logitech-g703.png), mapped to 046d:c087 / 046d:c090 and a G703 name fallback for shared Lightspeed receivers.
• Treat Primary/Logo lighting as RGB zones instead of a G502 X PLUS lightstrip: default to zone 0, and only apply the dark first-child chip when a hardware lightstrip is present.

Depends on the mouse-protocol G703 PR. Artwork is a Logitech G marketing render; confirm redistribution before a public package.

Test plan

• G703 on USB shows the G703 render in the device panel, not unknown-device.png
• Devices page lists G703 (wired) as supported
• Lighting picker shows Primary and Logo as equal zone chips (Primary is not a dark cluster chip)
• Selecting Logo still targets the logo zone
• G502 X PLUS lightstrip layout is unchanged