Type a payload's PayloadVersion as an integer

The key is typed in the plist, and each payload carried a string where
the top level carried an integer - which iOS may refuse outright. A test
now holds all three to the same type.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015GeH3y8fwTaTudaD88P57o

CHANGELOG.md

@@ -4,6 +4,10 @@ One line per change, grouped by the release that shipped it. Newest
 first. A release is a Cargo.toml bump plus a `v<version>` tag; the
 content repos pin the tag they run (see the end of this file).
 
+## 0.6.23 (2026-10-07)
+
+- A configuration profile's per-payload `PayloadVersion` is an integer, as the plist key is typed; it was a string, which iOS may refuse.
+
 ## 0.6.22 (2026-10-07)
 
 - `/profile.mobileconfig` renders an Apple configuration profile from the mail server's own PACC document (`profile.pacc` in `site.yaml`), so iOS can be set up in one install instead of probing for ports it cannot reach. Mail, CalDAV and CardDAV in one profile; every host, port and path from PACC, never written down twice; no address, username or password in the document, so one profile serves everyone and iOS asks at install; identifiers derived from the site, so reinstalling replaces the accounts rather than duplicating them (docs: content-reference, "A configuration profile").