feat(web): show app version in sidebar footer

Adds a small monospace �<InformationalVersion> line beneath the user
identity in MainLayout's sidebar footer. The full informational version
(including git sha after '+') is exposed via the title attribute for
hover inspection, while the displayed value is trimmed to the semver
prefix to stay compact.

The version is read once at component-class init from
typeof(MainLayout).Assembly's AssemblyInformationalVersionAttribute, so
it stays in sync with the centralized <Version> in Directory.Build.props
without any extra DI plumbing.

CSS: sidebar-footer becomes a flex column so user + version stack
cleanly with a small gap; the user line gets ellipsis to handle long
SamAccountNames.

Build 0/0, tests 50/50.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: robgrame

src/BitLockerKeyMonitor.Web/Components/Layout/MainLayout.razor

@@ -1,4 +1,5 @@
 @inherits LayoutComponentBase
+@using System.Reflection
 
 <div class="app-container">
     <nav class="sidebar">
@@ -33,9 +34,10 @@
         <div class="sidebar-footer">
             <Microsoft.AspNetCore.Components.Authorization.AuthorizeView>
                 <Authorized>
-                    <small>👤 @context.User.Identity?.Name</small>
+                    <small class="sidebar-footer-user">👤 @context.User.Identity?.Name</small>
                 </Authorized>
             </Microsoft.AspNetCore.Components.Authorization.AuthorizeView>
+            <small class="sidebar-footer-version" title="@_versionFull">v@_versionDisplay</small>
         </div>
     </nav>
 
@@ -52,3 +54,14 @@
     <a href="." class="reload">Reload</a>
     <span class="dismiss">🗙</span>
 </div>
+
+@code {
+    private static readonly string _versionFull =
+        typeof(MainLayout).Assembly
+            .GetCustomAttribute<AssemblyInformationalVersionAttribute>()?.InformationalVersion
+        ?? typeof(MainLayout).Assembly.GetName().Version?.ToString()
+        ?? "unknown";
+
+    private static readonly string _versionDisplay =
+        _versionFull.Split('+', 2)[0];
+}

src/BitLockerKeyMonitor.Web/wwwroot/app.css

@@ -72,7 +72,9 @@ code { background: #f1f3f5; padding: 0.1rem 0.4rem; border-radius: 4px; font-siz
 a { color: #3498db; }
 
 /* Sidebar footer */
-.sidebar-footer { position: absolute; bottom: 1rem; left: 1rem; right: 1rem; color: #888; font-size: 0.8rem; border-top: 1px solid #333; padding-top: 0.75rem; }
+.sidebar-footer { position: absolute; bottom: 1rem; left: 1rem; right: 1rem; color: #888; font-size: 0.8rem; border-top: 1px solid #333; padding-top: 0.75rem; display: flex; flex-direction: column; gap: 0.25rem; }
+.sidebar-footer-user { overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
+.sidebar-footer-version { color: #6c757d; font-size: 0.72rem; font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; letter-spacing: 0.02em; }
 
 /* Worker status badge (top bar of every page) + details modal */
 .app-topbar {