Release 0.8.0

The Windows installer has never shipped under a version: v0.7.0 was tagged
before any of it existed, so every build handed out so far stamped a server with
0.7.0. Two servers running different builds were indistinguishable, and the
installer logged each upgrade as "same version already installed" rather than
recording what changed. This cuts the release that fixes that.

0.8.0 rather than a patch: the air-gapped installer is a new capability, and
pre-1.0 semantic versioning puts that in the minor slot (ADR-007).

CHANGELOG gains a 0.8.0 section covering the twelve defects a real Windows
Server 2019 install surfaced, the move from inferring "is this a re-run of my
install?" to recording it, and the operator documentation.

deploy/site-profile-universal.json is now in the repository. Released builds
were being produced from a profile in a temporary directory, so the next release
could not have been reproduced once that file was cleaned up.
docs/RELEASING-WINDOWS.md points at the committed profile and says why.

scripts/gen_openapi.py reads __version__ out of shopdb/__init__.py instead of
restating it. Its hardcoded copy had already drifted a release behind, which is
the same mistake that once shipped an installer stamped with the wrong version.

frontend/package.json

@@ -1,6 +1,6 @@
 {
   "name": "shopdb-frontend",
-  "version": "0.7.0",
+  "version": "0.8.0",
   "private": true,
   "type": "module",
   "scripts": {