- Install @biomejs/biome@2.3.5 as unified linter and formatter
- Remove ESLint, Prettier and all related plugins (221 packages removed)
- Migrate linting rules from ESLint to Biome configuration
- Migrate formatting rules from Prettier to Biome configuration
- Exclude auto-generated proto files from linting (src/types/proto/**)
- Exclude CSS files from Biome (Tailwind syntax not yet supported)
- Update package.json scripts:
  - lint: tsc + biome check
  - lint:fix: biome check --write
  - format: biome format --write
- Auto-fix import organization across 60+ files
- Fix duplicate key in Russian locale (ru.json)
- Update CLAUDE.md documentation to reflect Biome usage

Benefits:
- 10-100x faster linting performance
- Simplified toolchain with single configuration file
- 221 fewer npm dependencies
- Unified linting, formatting, and import organization