[PM-43130] fix(importer): preserve 1pux vault structure as folders/collections on import

[matellis]

Closes #20724.

Problem

The 1pux importer discards all vault structure. Every item from every vault lands in a flat, unorganised list. A TODO comment in the parser marks where multi-vault handling was intended but never completed.

Change

• Pass each vault's attrs.name into processOverview as the folder name, for every vault regardless of type (Personal P, Everyone/Shared E, and user-created U vaults all hold real items).
• Items with tags get a nested folder VaultName/TagName; untagged items get VaultName.
• The org import path is unchanged at the call site -- moveFoldersToCollections already promotes vault folders to collections automatically.
• Removes the stale TODO comment and dead VaultAttributeTypeEnum reference (that enum was never defined).

Testing

• New unit tests: three-vault personal import across all vault types (P/E/U), org import collection mapping, tagged-item nesting.
• Existing folder/collection tests updated: SanitizedExport fixture items now land in "T's Test Vault/Movies" etc. instead of bare "Movies", and the second vault ("Personal") is correctly surfaced.

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[bitwarden-bot]

Thank you for your contribution! We've added this to our internal Community PR board for review.
ID: PM-43130
Link: https://bitwarden.atlassian.net/browse/PM-43130

Details on our contribution process can be found here: https://contributing.bitwarden.com/contributing/pull-requests/community-pr-process.