refactor: replace legacy flex utility classes and remove flex.scss

Replace all instances of prefixed flex utility classes (like flex-items-center, flex-justify-between, flex-full, flex-shrink-0) with their standard un-prefixed counterparts (items-center, justify-between, flex-1, shrink-0) across the codebase. Remove the deprecated src/static/scss/flex.scss partial file as it is no longer needed after these updates.

src/components/TopNavBar/index.vue

@@ -4,15 +4,15 @@
     <view :style="{ height: statusBarHeight + 'px' }" v-if="!hideStatusBar"></view>
 
     <!-- 导航栏内容 -->
-    <view class="flex flex-items-center flex-justify-between pl-[8px] pr-[8px]" :style="navContentStyle">
+    <view class="flex items-center justify-between pl-[8px] pr-[8px]" :style="navContentStyle">
       <!-- 左侧返回按钮 -->
-      <view class="nav-bar-left flex flex-items-center flex-justify-center" v-if="showBack" @click="handleBack">
+      <view class="nav-bar-left flex items-center justify-center" v-if="showBack" @click="handleBack">
         <uni-icons type="left" size="20" :color="backIconColor" />
       </view>
 
       <!-- 中间标题区域 -->
       <view :class="[
-        'nav-bar-center flex flex-items-center flex-justify-center',
+        'nav-bar-center flex items-center justify-center',
         `nav-bar-center--${titleAlign}`,
       ]">
         <slot name="title">