feat(phpipam): deploy phpIPAM for live IP address management

Lightweight IPAM with auto-discovery scanning every 15min via fping.
Replaces disabled NetBox (OOM'd). Uses existing MySQL InnoDB cluster
with Vault-rotated credentials. Cloudflare DNS + Authentik auth.

[ci skip]

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

stacks/phpipam/terragrunt.hcl

@@ -0,0 +1,8 @@
+include "root" {
+  path = find_in_parent_folders()
+}
+
+dependency "platform" {
+  config_path  = "../platform"
+  skip_outputs = true
+}