fix: repair two runtime bugs missed in Q2/Q3

- proxmox/__init__.py: re-export get_next_vmid, save_vm_instance,
  get_vm_instance so templates.py import doesn't raise ImportError
  (regression introduced in Q3 split)
- ipam.py:791: remove erroneous await on non-async get_orphan_allocations()
  (missed in Q2 async cleanup)

https://claude.ai/code/session_019rK2wvaWg5zXFwmAPPEB7R

backend/app/api/proxmox/__init__.py

@@ -4,6 +4,7 @@ from .sdn import router as sdn_router
 from .snapshots import router as snapshots_router
 from .vms import router as vms_router
 from .tasks import router as tasks_router
+from ._helpers import get_next_vmid, save_vm_instance, get_vm_instance
 
 router = APIRouter()
 router.include_router(servers_router)