Resolves (and creates if missing) the PhoenixKit Storage folder for a warehouse document.

Consolidates what were 5 near-identical *_storage_folders.ex modules in Andi (goods_issue_storage_folders.ex, goods_receipt_storage_folders.ex, inventory_storage_folders.ex, supplier_order_storage_folders.ex, internal_order_storage_folders.ex) into one module with 5 ensure_for_*/2 functions.

Layout: <prefix>-<number> (falling back to <prefix>-<uuid> when the document has no number yet), created under the parent folder returned by the optional host hook

config :phoenix_kit_warehouse, :storage_parent_folder, {MyApp.Media, :for_warehouse}

called as for_warehouse(resource, actor_uuid) with resource one of :goods_issue | :goods_receipt | :inventory | :supplier_order | :internal_order | :transfer, returning {:ok, parent_folder_uuid} or nil (= storage root, the default when the hook is absent). A hook that raises or returns something other than a UUID is logged and treated as nil. Lookup by name ignores trashed folders and checks the parent first, then the root; a root hit — or a cached folder still sitting at the root — is adopted (moved under the parent) so folders created before the hook existed keep their files. A failed move leaves the folder at the root.

Four of the five original resources (goods issue, goods receipt, inventory, supplier order) cache the resolved folder's uuid on a storage_folder_uuid column and take a fast path once cached. The fifth — internal orders — has no storage_folder_uuid column at all (confirmed: internal_order_storage_folders.ex is a genuine smaller variant with a single function clause and no write-back) and resolves by name on every call instead.

A sixth resource, transfers (added later, Plan 4/T15), also has a storage_folder_uuid column and follows the same cached fast-path as the four originals — see ensure_for_transfer/2.