update nvim plan9 theme, add hosts file, misc updates

- Port vacme colorscheme to plan9 with LazyVim extensions
- Add colorscheme switcher keymaps (plan9, acme, base16, catppuccin, tokyonight)
- Add StevenBlack-based hosts file (173K lines: ads, malware, tracking, gambling, porn)
- Add dkymap and webdev scripts, remove zed
- Minor fish config and picom updates