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/templates/index.html

@@ -21,13 +21,16 @@
   <!-- Header bar -->
   <header class="header-bar">
     <img src="/static/sovran-hub-icon.svg" alt="Sovran Hub" class="header-logo" />
-    <span class="title">Sovran_SystemsOS Hub</span>
-    
-    <!-- OS Version Badge -->
-    <span class="os-version-badge" id="os-version-badge" title="Sovran_SystemsOS Version">
-      <span class="version-label">v</span>
-      <span class="version-number" id="version-number">{{ sovran_version }}</span>
-    </span>
+
+    <div class="title-group">
+      <span class="title">Sovran_SystemsOS Hub</span>
+
+      <!-- OS Version Badge -->
+      <span class="os-version-badge" id="os-version-badge" title="Sovran_SystemsOS Version">
+        <span class="version-label">v</span>
+        <span class="version-number" id="version-number">{{ sovran_version }}</span>
+      </span>
+    </div>
 
     <div class="header-buttons">
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