fix(hub): resolve 'vdev' version badge and align it under the Hub title

- The Hub header badge could render 'vdev' because the runtime
  /etc/nixos/VERSION lookup fell back to the literal string 'dev' when
  the file was missing (e.g. dev/test environments, or before the
  Nix-generated config carried a version at all).
- modules/core/sovran-hub.nix now reads the repo's VERSION file at
  Nix eval time and bakes a real semantic version (sovran_version)
  into the generated config.json and a VERSION file shipped with the
  package, so the Hub always has a solid value to display.
- server.py's _get_sovran_version() now reads that baked-in
  sovran_version first, and explicitly rejects a literal 'dev' value
  from any of its file-based fallbacks so the badge never shows
  'vdev' again.
- templates/index.html + header.css: wrapped the title and the
  version badge in a '.title-group' column so the version badge sits
  directly underneath 'Sovran_SystemsOS Hub', left-aligned with it.

Co-authored-by: arena-agent <297053741+arena-agent@users.noreply.github.com>

app/sovran_systemsos_web/static/css/header.css

@@ -29,6 +29,14 @@
   color: var(--text-primary);
 }
 
+.title-group {
+  display: flex;
+  flex-direction: column;
+  align-items: flex-start;
+  justify-content: center;
+  gap: 2px;
+}
+
 .header-buttons {
   display: flex;
   align-items: center;
@@ -58,8 +66,8 @@
   color: #4ade80;
   box-shadow: 0 2px 4px rgba(0, 0, 0, 0.2);
   transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
-  margin-left: 12px;
   white-space: nowrap;
+  align-self: flex-start;
 }
 
 .os-version-badge:hover {