feat: automated s3 backup

[affeldt28]

Documents the new volume and system backup functionality introduced in getarcaneapp/arcane#3459.

Addresses getarcaneapp/arcane#3194.

[Copilot]

Pull request overview

Adds documentation for Arcane’s new volume and system backup functionality (including S3-compatible destinations) and wires the new docs page into the Features navigation.

Changes:

• Adds a new Backups feature doc covering local storage, S3 destinations, scheduling/retention, encryption, and restore flows.
• Updates the existing Volumes doc to reflect the new Rustic-based backup model and links to the new Backups page.
• Adds the new Backups page to the docs sidebar navigation under Features.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
src/lib/config/docs.ts	Adds the features/backups doc leaf to the Features nav group.
content/features/volumes.md	Replaces the old tar-based backup description with Rustic snapshot workflow and links to the Backups doc.
content/features/backups.md	New comprehensive Backups doc for volume backups and Arcane system backups (local + S3).

Comments suppressed due to low confidence (1)

content/features/backups.md:52

• This callout uses "local repository" without context; it’s easy to misread as the source-code repository. Clarify that it refers to the local backup repository stored under /backups.

> A local backup on the same host does not protect against disk or host failure. Use S3 or copy the local repository to another system for off-site recovery.

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[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.