feat: add ASCII art email signature and update documentation

- Add signature.txt with stylish VALKNAR banner and contact info
- Update README.md to document the new signature file
- Clean up .gitignore to track signature.txt
- Remove legacy config files (prettier, rubocop, pre-commit, etc.)
- Update arty.yml with additional installation scripts

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

.gitignore

@@ -8,32 +8,18 @@
 !.gitmodules
 !README.md
 !.editorconfig
-!.prettierrc
-!.prettierignore
-!package.json
-!pnpm-workspace.yaml
 !.nvmrc
 !.ruby-version
 !.python-version
-!.pre-commit-config.yaml
-!.rubocop.yml
-!requirements.txt
-!Gemfile
-!ecosystem.config.js
-!playbook.yml
 !.p10k.zsh
-!crates.yml
-!flatpaks.yml
-!eslint.config.mts
 !.zprofile
 !.zlogout
 !.zlogin
 !.zshrc
 !.zshenv
 !.hushlogin
-!.last_pwd
-!biome.json
 !arty.yml
+!signature.txt
 
 !/.config/
 !/.config/zed/