docs: fix install example indentation, add Podman, nest platform tabs

[enoch85]

Fixes Maintainerr/Maintainerr#3752.

Change	Detail
Indentation	MDX strips leading indentation from multi-line template literals inside a JSX attribute, which is why the Compose (and docker run) examples rendered flush left. Samples now live in export const blocks and are passed by name.
Podman	New Podman tab with the Quadlet unit from the app README, start commands, rootful note and an update step.
Layout	Install section is nested tabs: Docker / Podman / Kubernetes, then Compose / Run / Update, Quadlet / Update, Manifest / Update. The separate Updating sections moved into the Update tabs.
Collections.md	Anchor updated from #docker to #install.

Note: /installation/ serves the last released version, so the fix reaches that URL at the next release; it is live under /next/installation/ immediately.