fix(vm_provision_mixin): storage 'enabled' absent means enabled, not disabled

Proxmox's /storage API omits the "enabled" key entirely for storages that
were never explicitly toggled, rather than defaulting it to 1 — it isn't
present-and-falsy, it's just absent. Both _find_default_image_storage and
the snippet-storage discovery treated storage.get("enabled") as truthy-check,
so every storage without an explicit "enabled": 1 was silently excluded.

Confirmed live against a real Proxmox test server: local-lvm, local-zfs, and
fast-zfs all had content=images with no "enabled" key at all, causing
create_vm_from_cloud_init to always fail with "No storage with
content='images' found" despite multiple valid storages existing. All prior
tests used "enabled": 1 explicitly in their fixtures, masking the bug.

Fix: storage.get("enabled", 1) != 0 — absent or truthy means enabled, only
an explicit 0 excludes it. 4 new regression tests, 28 total pass.

napalm_proxmox/vm_provision_mixin.py

@@ -102,10 +102,15 @@ class ProxmoxVMProvisionMixin:
         return local_path
 
     def _find_default_image_storage(self) -> str:
-        """Find a storage suitable for VM root disks (content includes 'images')."""
+        """Find a storage suitable for VM root disks (content includes 'images').
+
+        Proxmox's /storage API omits the "enabled" field entirely for storages
+        that were never explicitly toggled — it is not present-and-falsy, it is
+        just absent, defaulting to enabled. Only an explicit 0 means disabled.
+        """
         for storage in self._api.storage.get():
             content = storage.get("content", "")
-            if "images" in content and storage.get("enabled"):
+            if "images" in content and storage.get("enabled", 1) != 0:
                 return storage["storage"]
         raise ValueError(
             "No storage with content='images' found. Configure a storage for VM disks."
@@ -266,12 +271,13 @@ class ProxmoxVMProvisionMixin:
             self._node_api().qemu(vmid).config.post(**config_args)
 
             # Step 5: Verify snippet storage exists
+            # (enabled is absent-not-falsy on Proxmox — see _find_default_image_storage)
             _logger.info("Checking for snippet storage...")
             storages = self._api.storage.get()
             snippet_storage = None
             for storage in storages:
                 content = storage.get("content", "")
-                if "snippets" in content and storage.get("enabled"):
+                if "snippets" in content and storage.get("enabled", 1) != 0:
                     snippet_storage = storage["storage"]
                     break