case 4759 - upgrade from 8.2.4 or older: reminder of the 8.3.0 pre-upgrade step, Linux upgrade scripts check for the .NET 10 runtime

The upgrade overview page has a section for upgrades from 8.2.4 or older, and
the 8.3.1 changelog section opens with a line pointing to it (the "new version
available" notice links to the newest section); the release procedure's
version bump now carries that line into each new section. Both Linux upgrade
scripts first check for the .NET 10 ASP.NET Core runtime and stop with nothing
changed if it is missing (tested on devtest: present, dotnet not found, only
an older runtime). The desktop script's download now uses curl -f, as the
server's does since case 4727, so a failed download stops before files are
removed.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

devdocs/build/RELEASE-PROCEDURE.md

@@ -257,7 +257,7 @@ new code. Set the new version in:
 | raven | `dist/install/windows/x64/lan.iss` | `#define MyAppVersion` |
 | raven | `dist/install/windows/x64/standalone.iss` | `#define MyAppVersion` |
 | raven | `dist/latest-version.json` | `latestversion` and the `changelogurl` anchor |
-| raven | `docs/8.0/ayanova/docs/changelog.md` | new version heading with "IN PROGRESS" under it |
+| raven | `docs/8.0/ayanova/docs/changelog.md` | new version heading; under it the "Upgrading from 8.2.4 or older?" line copied from the previous version's section (case 4759; keep it until John decides enough customers are past 8.3.0), then "IN PROGRESS" |
 | raven | `docs/8.0/ayanova/docs/ay-about.md` | the example version number |
 | raven-client | `ayanova/package.json`, `ayanova/package-lock.json` | `"version"` (both places in the lock file) |
 | raven-client | `ayanova/src/api/ayanova-version.js` | `version` |