Add version numbering (v1.0.0)

- package.json: bump to 1.0.0
- server/config.js: export APP_VERSION (from package.json) and GIT_COMMIT
  (from COMMIT_SHA env var set by CI, or git rev-parse --short HEAD fallback)
- GET /api/version: new public endpoint returning { version, commit }
- GET /api/admin-auth/status: includes version and commit in response
- AdminPage sidebar: displays version string (e.g. "v1.0.0 (1d43875)")
  below the Log Out button, styled as muted metadata text

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/App.css

@@ -7203,6 +7203,13 @@
     color: var(--brand-warm-white);
   }
 
+  .admin-sidebar-version {
+    padding: 0.5rem 1.1rem 0.75rem;
+    font-size: 0.72rem;
+    color: rgba(240,234,216,0.28);
+    letter-spacing: 0.04em;
+  }
+
   .admin-nav-search {
     display: grid;
     gap: 0.4rem;