Add cheatsheets section (Proxmox CLI, zsh config reference)

Lower-bar reference material, distinct from docs/'s engineering write-ups:
recovered Proxmox cheat sheets (live-verified against PVE 9.2.21, new
remote-migrate/importovf/pvesm subcommands added, acmedomain0 flag typo
fixed) plus the real zsh aliases/functions/keybindings from the actual
ZDOTDIR-based config.

README.md

@@ -135,6 +135,12 @@ A self-hosted WireGuard mesh gives every fleet host and personal device its own
 
 ---
 
+## Cheatsheets
+
+Quick-reference material for tools I use day-to-day — command references and config notes, not full write-ups. See [`cheatsheets/`](cheatsheets/).
+
+---
+
 ## Scripts & Tooling
 
 A few standalone scripts live in [`projects/`](projects/) alongside the Docker stacks — real tooling, not demo code: