Add AlphaPulse brand icon across the web app

Use a shared SVG combining an A mark with a market pulse line for the favicon, login page, and navigation. Preserve the existing theme and page layout.

web/src/common/components/AppLayout/index.vue

@@ -1,5 +1,5 @@
 <script lang="ts" setup>
-import { SwitchButton, TrendCharts } from "@element-plus/icons-vue"
+import { SwitchButton } from "@element-plus/icons-vue"
 import { useUserStore } from "@/pinia/stores/user"
 import { menuRoutes } from "@/router/routes"
 
@@ -16,9 +16,7 @@ async function logout() {
   <div class="h-full flex flex-col">
     <header class="app-header h-auto flex shrink-0 flex-wrap items-center gap-x-3 gap-y-0 border-b border-b-slate-200 border-b-solid bg-white px-3 pt-2 shadow-sm lg:h-14 lg:flex-nowrap lg:gap-6 lg:px-6 lg:pt-0">
       <div class="brand flex flex-1 shrink-0 items-center gap-2 text-base lg:flex-none lg:text-lg text-slate-900 font-bold">
-        <el-icon :size="22" color="var(--el-color-primary)">
-          <TrendCharts />
-        </el-icon>
+        <img src="/favicon.svg" alt="" aria-hidden="true" width="24" height="24" class="shrink-0">
         AlphaPulse
       </div>
       <nav class="app-nav order-4 h-10 min-w-0 flex flex-1 basis-full gap-5 overflow-x-auto text-sm lg:order-none lg:h-full lg:basis-auto lg:gap-6">

web/src/pages/login/index.vue

@@ -1,7 +1,6 @@
 <script lang="ts" setup>
 import type { FormInstance, FormRules } from "element-plus"
 import { getCaptchaApi, loginApi } from "@@/apis/auth"
-import { TrendCharts } from "@element-plus/icons-vue"
 import axios, { CanceledError } from "axios"
 import { useUserStore } from "@/pinia/stores/user"
 import { safeRedirect } from "@/router/guards"
@@ -96,9 +95,7 @@ async function submit() {
     <el-card class="w-90" shadow="never" body-class="px-8 pb-8 pt-6">
       <div class="mb-6 text-center">
         <div class="flex-center gap-2 text-2xl text-slate-900 font-bold">
-          <el-icon :size="26" color="var(--el-color-primary)">
-            <TrendCharts />
-          </el-icon>
+          <img src="/favicon.svg" alt="" aria-hidden="true" width="32" height="32" class="shrink-0">
           AlphaPulse
         </div>
         <div class="mt-1 text-xs text-slate-500">