feat(ui): 统一应用主题色为天空蓝并优化渐变背景

将应用主色调从 '#BBF246' 更改为 '#87CEEB'（天空蓝），并更新所有相关组件和页面中的颜色引用。同时为多个页面添加统一的渐变背景，提升视觉效果和用户体验。新增压力分析模态框组件，并优化压力计组件的交互与显示逻辑。更新应用图标和启动图资源。

app/(tabs)/personal.tsx

@@ -9,6 +9,7 @@ import { Ionicons } from '@expo/vector-icons';
 import AsyncStorage from '@react-native-async-storage/async-storage';
 import { useBottomTabBarHeight } from '@react-navigation/bottom-tabs';
 import { useFocusEffect } from '@react-navigation/native';
+import { LinearGradient } from 'expo-linear-gradient';
 import React, { useMemo, useState } from 'react';
 import { Alert, Image, Linking, SafeAreaView, ScrollView, StatusBar, StyleSheet, Switch, Text, TouchableOpacity, View } from 'react-native';
 import { useSafeAreaInsets } from 'react-native-safe-area-context';
@@ -287,11 +288,17 @@ export default function PersonalScreen() {
   ];
 
   return (
-    <View style={[styles.container, { backgroundColor: theme === 'light' ? colorTokens.pageBackgroundEmphasis : colorTokens.background }]}>
+    <View style={styles.container}>
+      <LinearGradient
+        colors={[colors.backgroundGradientStart, colors.backgroundGradientEnd]}
+        style={styles.gradientBackground}
+        start={{ x: 0, y: 0 }}
+        end={{ x: 0, y: 1 }}
+      />
       <StatusBar barStyle={'dark-content'} backgroundColor="transparent" translucent />
-      <SafeAreaView style={[styles.safeArea, { backgroundColor: theme === 'light' ? colorTokens.pageBackgroundEmphasis : colorTokens.background }]}>
+      <SafeAreaView style={styles.safeArea}>
         <ScrollView
-          style={[styles.scrollView, { backgroundColor: theme === 'light' ? colorTokens.pageBackgroundEmphasis : colorTokens.background }]}
+          style={styles.scrollView}
           contentContainerStyle={{ paddingBottom: bottomPadding }}
           showsVerticalScrollIndicator={false}
         >
@@ -311,6 +318,13 @@ const styles = StyleSheet.create({
   container: {
     flex: 1,
   },
+  gradientBackground: {
+    position: 'absolute',
+    left: 0,
+    right: 0,
+    top: 0,
+    bottom: 0,
+  },
   safeArea: {
     flex: 1,
   },