Blancco: playbook now produces working Ubuntu-kernel initramfs out of the box

Companion to the previous commit (4550d43). Three files that should have
been in the same commit but got left out of `git add`:

- .gitignore: negate rule for boot-tools/blancco/grub-blancco.cfg so the
  tracked cfg (source of truth for grubx64.efi rebuilds) survives
  the blanket boot-tools/ ignore.

- playbook/blancco-init.sh: rewritten for modprobe-with-deps, full NIC
  driver coverage, set -x trace to /dev/console, dmesg + PCI-device +
  /proc/modules dump + interactive shell on "no NIC after 60s".
  Replaces the narrow insmod-loop version that silently hung on
  unsupported NICs.

- playbook/pxe_server_setup.yml "Build Blancco PXE initramfs" task now
  sweeps the full drivers/net/ tree (ethernet + phy + mdio + usb + fddi
  + wan) plus overlay / squashfs / loop / ptp / libphy / mii deps, runs
  depmod to regenerate modules.dep inside the initramfs (required for
  modprobe dependency resolution), and symlinks the full applet list
  blancco-init.sh needs (modprobe, insmod, dmesg, find, env, etc).
  Result: ~20 MB initramfs vs the old 2 MB narrow build.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.gitignore

@@ -24,6 +24,9 @@ offline-packages/
 
 # Boot tool binaries (built by prepare-boot-tools.sh)
 boot-tools/
+# Track the Blancco GRUB config as source-of-truth for grubx64.efi rebuilds.
+# prepare-boot-tools.sh rebuilds grubx64.efi from this file via grub-mkstandalone.
+!boot-tools/blancco/grub-blancco.cfg
 
 # WinPE boot files (wimboot, boot.wim, BCD, ipxe.efi, etc.)
 boot-files/
@@ -54,23 +57,23 @@ secrets.md
 enrollment/
 drivers-staging/
 bios-staging/
-.claude/
-
-# Secrets and credentials (defensive)
-.env
-.env.*
-!.env.example
-!.env.*.example
-*.pem
-*.key
-id_rsa
-id_rsa.*
-*.ppk
-*.p12
-*.pfx
-secrets.json
-secrets.yaml
-secrets.yml
-*_secret
-*_secrets
-credentials.json
+.claude/
+
+# Secrets and credentials (defensive)
+.env
+.env.*
+!.env.example
+!.env.*.example
+*.pem
+*.key
+id_rsa
+id_rsa.*
+*.ppk
+*.p12
+*.pfx
+secrets.json
+secrets.yaml
+secrets.yml
+*_secret
+*_secrets
+credentials.json