Document TrueNAS Apps Market install path

[ggfevans]

Context

Rackula is listed in the TrueNAS Apps Market community catalogue:

• https://apps.truenas.com/catalog/rackula_community/

The docs currently cover Docker self-hosting, and issue #23 covers Proxmox/LXC. TrueNAS users should also have a discoverable install path in the self-hosting docs, since Rackula is now available through the TrueNAS Apps Market.

Proposed work

Add TrueNAS install documentation under src/content/docs/self-hosting/, either as a new page such as truenas.mdx or as a clearly linked section from the existing self-hosting docs.

Include:

• A short explanation of when to use the TrueNAS Apps Market install path versus Docker.
• A link to the TrueNAS Rackula catalogue page.
• Basic install flow from the TrueNAS UI: Apps → Discover Apps / Catalog → search for Rackula → Install.
• Current catalogue details worth documenting or verifying while writing:
  • train: Community
  • app version shown at issue creation: 26.6.6
  • app category: productivity
  • default WebUI port: 30323
  • containers: rackula and rackula-api
  • run-as user/group defaults: 568 / apps
  • configurable groups include Rackula, user/group, network, storage, labels, and resources
• Note the current CORS Origin migration/deprecation notice from the catalogue page, especially that wildcard CORS Origin is no longer supported.
• Expected post-install steps: where to open the WebUI, what persistence/API behaviour users should expect, and any TrueNAS-specific storage or networking choices that differ from Docker.
• Links from relevant entry points, likely the docs home page self-hosting card and/or the Docker deployment page.

Acceptance criteria

• TrueNAS is capitalised correctly throughout.
• Uses Canadian/British spelling where applicable.
• TrueNAS install path is discoverable from the self-hosting docs.
• The page distinguishes the official TrueNAS Apps Market flow from the generic Docker deployment path.
• npm run build passes.