feat(layout): add russian+qwerty layout (@cgcormier)

[cgcormier]

Description

The Russian keymap only defines its normal and Shift legends, so it has nothing to display when the alternate layer is selected.

This adds the suggested ANSI russian+qwerty layout:

• Russian labels for the normal and Shift layers
• QWERTY labels for the alternate and Shift+alternate layers

Keys are paired by physical position. The existing russian and qwerty layouts remain unchanged.

Checks

• Adding a layout?
  • Followed the layouts documentation
  • Added the layout to packages/schemas/src/layouts.ts
  • Added the layout JSON to frontend/static/layouts
• Checked for related open issues
• Used the required Conventional Commits PR title
• Included the GitHub username in the PR title
• Verified formatting with Oxfmt
• Verified JSON parsing, ANSI row sizes, four-layer legends, exact positional pairing, and registry/file parity
• Verified git diff --check

Closes #8222