feat(admin): display running version in footer and /health

Inline package.json version at bundle time via src/config/version.ts
(resolveJsonModule), surface it in the shared admin/status footer and
add it to the /health JSON so self-hosters can tell which build runs.

Co-Authored-By: Claude Opus 4.7 <[email protected]>

src/styles/layout.css

@@ -247,3 +247,8 @@
 .site-footer-sponsor:hover {
   color: #db61a2 !important;
 }
+
+.site-footer-version {
+  font-variant-numeric: tabular-nums;
+  opacity: 0.7;
+}