feat: automated stable releases, versioned ISOs, and Hub version badge

- Add release-stable.sh script with automatic tagging, CHANGELOG updates,
  GitHub/Gitea release creation, and VERSION file management
- Update iso/common.nix to include version from VERSION file in ISO filename
- Add VERSION file (current: 1.0.3)
- Polish OS version badge in Sovran Hub header (top-right)
- Update README.md download link to versioned ISO
- Update CHANGELOG.md with existing tags (v1.0.0 – v1.0.3)

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

app/sovran_systemsos_web/templates/index.html

@@ -22,6 +22,13 @@
   <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="header-buttons">
       <span class="role-badge" id="role-badge">Loading…</span>
       <button class="btn btn-header-reboot" id="btn-header-reboot" title="Restart the entire computer">Reboot</button>