[3.2] Add linting config templates

[vbonk]

What needs to be done

Create templates/linting/ with: eslint.config.mjs.template, ruff.toml.template, .golangci.yml.template, rustfmt.toml.template.

Acceptance Criteria

• 4 template files in templates/linting/
• Each has sensible defaults
• init-template copies relevant one to root

[vbonk]

Completed in Phase 3 PR #85.