feat(mobile): update DocuElevate mobile app branding with original logo and UX

- Regenerate all app icons (icon.png, adaptive-icon.png, splash.png,
  favicon.png, notification-icon.png) using the DocuElevate folder+gear
  SVG logo on brand blue (#1e40af) background
- Add assets/logo.png (200×200 circular logo) for the login screen
- Update LoginScreen.tsx to display the DocuElevate logo image above
  the brand name text instead of plain text only
- Replace emoji tab bar icons (⬆️📄👤) with Ionicons vector icons
  (cloud-upload-outline, document-text-outline, person-circle-outline)
  from the already-installed @expo/vector-icons package

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

mobile/App.tsx

@@ -8,6 +8,7 @@
 
 import { NavigationContainer } from "@react-navigation/native";
 import { createBottomTabNavigator } from "@react-navigation/bottom-tabs";
+import { Ionicons } from "@expo/vector-icons";
 import React from "react";
 import { ActivityIndicator, StyleSheet, Text, View } from "react-native";
 import { SafeAreaProvider } from "react-native-safe-area-context";
@@ -48,8 +49,8 @@ function TabNavigator() {
         options={{
           title: "Upload",
           tabBarLabel: "Upload",
-          tabBarIcon: ({ color }) => (
-            <Text style={{ fontSize: 20, color }}>⬆️</Text>
+          tabBarIcon: ({ color, size }) => (
+            <Ionicons name="cloud-upload-outline" size={size} color={color} />
           ),
           headerTitle: "DocuElevate",
         }}
@@ -60,8 +61,8 @@ function TabNavigator() {
         options={{
           title: "Files",
           tabBarLabel: "Files",
-          tabBarIcon: ({ color }) => (
-            <Text style={{ fontSize: 20, color }}>📄</Text>
+          tabBarIcon: ({ color, size }) => (
+            <Ionicons name="document-text-outline" size={size} color={color} />
           ),
           headerTitle: "My Documents",
         }}
@@ -72,8 +73,8 @@ function TabNavigator() {
         options={{
           title: "Profile",
           tabBarLabel: "Profile",
-          tabBarIcon: ({ color }) => (
-            <Text style={{ fontSize: 20, color }}>👤</Text>
+          tabBarIcon: ({ color, size }) => (
+            <Ionicons name="person-circle-outline" size={size} color={color} />
           ),
           headerTitle: "Profile",
         }}