优化 AddDownloadDialog 组件的样式，调整下载器和保存目录选择器的显示效果

src/components/dialog/AddDownloadDialog.vue

@@ -127,7 +127,6 @@ onMounted(() => {
       </VCardTitle>
       <DialogCloseBtn @click="emit('close')" />
       <VDivider />
-      <VCardText class="p-1">
       <VList lines="one">
         <VListItem>
           <template #prepend>
@@ -160,14 +159,16 @@ onMounted(() => {
           </VListItemTitle>
         </VListItem>
       </VList>
-        <VRow>
+      <VRow class="px-7">
         <VCol cols="12" md="4">
           <VSelect
             v-model="selectedDownloader"
             :items="downloaderOptions"
+            size="small"
             label="下载器（默认）"
             variant="underlined"
             placeholder="留空默认"
+            density="compact"
           />
         </VCol>
         <VCol cols="12" md="8">
@@ -175,12 +176,13 @@ onMounted(() => {
             v-model="selectedDirectory"
             :items="targetDirectories"
             label="保存目录（自动）"
+            size="small"
             placeholder="留空自动匹配"
             variant="underlined"
+            density="compact"
           />
         </VCol>
       </VRow>
-      </VCardText>
       <VCardText class="text-center">
         <VBtn variant="elevated" :disabled="loading" @click="addDownload" :prepend-icon="icon" class="px-5">
           {{ buttonText }}