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

android/app/src/main/AndroidManifest.xml

@@ -0,0 +1,26 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android">
+
+    <uses-permission android:name="android.permission.INTERNET" />
+    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
+
+    <application
+        android:name=".ServerManagerApp"
+        android:allowBackup="true"
+        android:icon="@mipmap/ic_launcher"
+        android:label="@string/app_name"
+        android:supportsRtl="true"
+        android:theme="@style/Theme.ServerManager"
+        android:usesCleartextTraffic="true">
+
+        <activity
+            android:name=".MainActivity"
+            android:exported="true"
+            android:theme="@style/Theme.ServerManager.Splash">
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN" />
+                <category android:name="android.intent.category.LAUNCHER" />
+            </intent-filter>
+        </activity>
+    </application>
+</manifest>