Add Oh My Zsh as git submodule with enhanced plugin configuration

- Add Oh My Zsh as submodule at zsh/oh-my-zsh
- Update ZSH path to use dotfiles submodule
- Add 14 useful plugins including autosuggestions, syntax highlighting, docker, tmux, and z
- Configure Oh My Zsh settings (disable auto-update, enable correction, etc.)
- Add plugin customizations for autosuggestions and history-substring-search
- Integrate Spaceship prompt with Oh My Zsh

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

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

.gitmodules

@@ -1,3 +1,6 @@
 [submodule "zsh/spaceship-prompt"]
 	path = zsh/spaceship-prompt
 	url = https://github.com/spaceship-prompt/spaceship-prompt.git
+[submodule "zsh/oh-my-zsh"]
+	path = zsh/oh-my-zsh
+	url = https://github.com/ohmyzsh/ohmyzsh.git