feat(railiance): implement CUST-WP-0032 Haskell build machine infra

Packer build definition, cloud-init autoinstall, GHCup toolchain script,
boot-time registration agent (state-hub + autossh dual tunnel), systemd
unit, key injection, remote-build Makefile, smoke test, and deployment
README. All 15 tasks complete.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

infra/build-machines/port-registry.yml

@@ -0,0 +1,37 @@
+# Build machine port registry
+# Range: 12221-12230 (10 slots)
+# Each entry: port, vm_name, host_machine, status
+
+ports:
+  12221:
+    vm_name: haskell-build-alpha
+    host_machine: unassigned
+    status: reserved
+  12222:
+    vm_name: haskell-build-beta
+    host_machine: unassigned
+    status: reserved
+  12223:
+    vm_name: unassigned
+    status: available
+  12224:
+    vm_name: unassigned
+    status: available
+  12225:
+    vm_name: unassigned
+    status: available
+  12226:
+    vm_name: unassigned
+    status: available
+  12227:
+    vm_name: unassigned
+    status: available
+  12228:
+    vm_name: unassigned
+    status: available
+  12229:
+    vm_name: unassigned
+    status: available
+  12230:
+    vm_name: unassigned
+    status: available