feat: 标题栏和占位图使用 icon.svg 替代 JRD 文字

src/renderer/src/components/MainArea.vue

@@ -258,7 +258,7 @@ onUnmounted(() => {
         <MemoryAnalysis v-else-if="activeTab.type === 'memory'" />
       </template>
       <div v-if="!connStore.isConnected" class="no-connection">
-        <div class="placeholder-icon">JRD</div>
+        <img src="/icon.svg" class="placeholder-icon" alt="JRedisDesktop" />
         <h2>JRedisDesktop</h2>
         <p>{{ t('app.placeholder') }}</p>
       </div>
@@ -516,19 +516,11 @@ onUnmounted(() => {
 }
 
 .placeholder-icon {
-  width: 80px;
-  height: 64px;
-  background: linear-gradient(135deg, #667eea, #764ba2);
-  border-radius: 16px;
-  display: flex;
-  align-items: center;
-  justify-content: center;
-  font-size: 22px;
-  font-weight: 800;
-  color: #fff;
+  width: 96px;
+  height: 96px;
+  border-radius: 20px;
   margin-bottom: 20px;
   box-shadow: 0 8px 32px rgba(99, 102, 241, 0.2);
-  letter-spacing: 1px;
 }
 
 .no-connection h2 {

src/renderer/src/components/TitleBar.vue

@@ -22,7 +22,7 @@ function openSettings() {
 <template>
   <header class="titlebar">
     <div class="titlebar-drag">
-      <span class="titlebar-logo">JRD</span>
+      <img src="/icon.svg" class="titlebar-logo" alt="JRedisDesktop" />
       <span class="titlebar-title">JRedisDesktop</span>
     </div>
     <div class="titlebar-actions">
@@ -60,17 +60,10 @@ function openSettings() {
 }
 
 .titlebar-logo {
-  width: 36px;
+  width: 24px;
   height: 24px;
-  background: linear-gradient(135deg, #667eea, #764ba2);
   border-radius: 6px;
-  display: flex;
-  align-items: center;
-  justify-content: center;
-  font-size: 9px;
-  font-weight: 800;
-  color: #fff;
-  letter-spacing: 0.5px;
+  flex-shrink: 0;
 }
 
 .titlebar-title {