chore: update git configuration and remove unused files

- Updated Git user email in `.gitconfig`.
- Removed obsolete Kitty and Topgrade configuration files.
- Cleaned up Zsh configuration by removing unused snippets and scripts, and reorganized plugin loading in `.zshrc`.

zsh/.zshenv

@@ -1,3 +1,3 @@
-export XDG_CONFIG_HOME="${HOME}/.config"
-export ZDOTDIR="${XDG_CONFIG_HOME}/zsh"
-export SHELL_SESSIONS_DISABLE=1
+XDG_CONFIG_HOME="${HOME}/.config"
+XDG_BIN_HOME="${HOME}/.local/bin"
+ZDOTDIR="${XDG_CONFIG_HOME}/zsh"