restructure: move proxmox/ into subfolder, add pihole/ section

All existing content moved from repo root into proxmox/ to make room
for other Debian machine configs. Adds pihole/ with:

- config/pihole.toml — snapshot of current Pi-hole v6 config
- config/dnsmasq.d/99-ipxe-chainload.conf — custom PXE DHCP rules
  (EFI/BIOS iPXE chainload, fixed tag-specificity bug for UEFI boot)
- pull-config.sh <source-host> <dest-dir> — pull live config to disk
- apply-config.sh <source-dir> <dest-host> — push config to a Pi-hole

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XRzqNDrbnYR22ZgZj1Bg3s

pihole/config/dnsmasq.d/99-ipxe-chainload.conf

@@ -0,0 +1,20 @@
+# Detect iPXE clients (already running iPXE).
+dhcp-match=set:ipxe,175
+dhcp-userclass=set:ipxe,iPXE
+
+# Detect UEFI x86_64 clients by client architecture.
+dhcp-match=set:efi64,option:client-arch,7
+dhcp-match=set:efi64,option:client-arch,9
+
+# Boot file selection — more positive tags = higher priority.
+# EFI iPXE (2 tags): already running iPXE on EFI, chain to HTTP menu.
+dhcp-boot=tag:ipxe,tag:efi64,http://192.168.2.247/boot.ipxe
+
+# BIOS iPXE (1 tag): already running iPXE, chain to HTTP menu.
+dhcp-boot=tag:ipxe,http://192.168.2.247/boot.ipxe
+
+# EFI non-iPXE (1 tag): send the EFI iPXE binary.
+dhcp-boot=tag:efi64,ipxe.efi,,192.168.2.247
+
+# BIOS/legacy fallback (0 tags): send the BIOS iPXE binary.
+dhcp-boot=undionly.kpxe,,192.168.2.247