feat: redesign Android app with animations, charts, profile, and registration

- Register screen with validation (username, email, password, confirm)
- Profile screen with email editing and password change
- User greeting on dashboard showing logged-in username
- 401 auto-logout via SessionManager + AuthInterceptor
- MetricsChart with Canvas line graphs (CPU, RAM, Disk)
- Animated StatCard with counters and icons
- ServerCard with progress bars, pulsating status dot, dynamic elevation
- Shimmer loading placeholders
- Dark mode support with Material3
- Navigation transitions (slide + fade)
- New server rack launcher icon
- Splash screen
- Backend API: register, profile (GET/PUT) endpoints

views/dashboard/index.php

@@ -52,6 +52,13 @@ $recentActivity = $recentActivity ?? [];
             <span class="stat-label">Avg Disk</span>
         </div>
     </div>
+    <a href="/sysadmin.apk" class="stat-card stat-card-info" download style="text-decoration:none; cursor:pointer;">
+        <div class="stat-icon"><i class="fas fa-download"></i></div>
+        <div class="stat-info">
+            <span class="stat-value">v1.0</span>
+            <span class="stat-label">Android App</span>
+        </div>
+    </a>
 </div>
 
 <div class="dashboard-grid">