## Description
The dashboard "update to vX.Y.Z is available" banner is a self-hosted
upgrade nudge, but nothing gates it to self-hosted installs. On a
managed cloud instance the banner can still appear:
`latest_chatwoot_version` is populated in Redis from the hub's
advertised latest stable release, and the frontend compares it
(`semver.lt`) against the per-request `appVersion` baked into the
dashboard HTML. When a browser session is holding HTML rendered before
the current deploy, `appVersion` lags the hub's advertised version and
the banner fires, even though the managed instance is already on the
newest build.
This gates the value at the source: `api/v1/accounts#show` no longer
sets `latest_chatwoot_version` when running on cloud, so
`hasAnUpdateAvailable` short-circuits (`semver.valid(null)` is false)
and the banner never renders there. Self-hosted behaviour is unchanged.
Fixes https://linear.app/chatwoot/issue/CW-7763
d5f7a2be64