style: 全局 UI 主题皮肤重构与样式模块化

引入 Element Plus 主题定制和主题皮肤 composable，将全局
样式拆分为组件级独立 CSS 文件（侧边栏、顶栏、工作台等），
统一色彩变量和间距规范，重构所有视图和组件样式以适配新
主题系统，优化图表和知识图谱组件视觉表现，提取审计和差
旅报销相关子组件。

web/src/views/ArchiveCenterView.vue

@@ -29,35 +29,35 @@
             <input v-model="listKeyword" type="search" placeholder="搜索单号、申请人、部门、归档类型..." />
           </div>
 
-          <div
-            v-for="dropdown in filterDropdowns"
-            :key="dropdown.key"
-            class="archive-dropdown-filter"
-            :class="{ open: openFilterKey === dropdown.key }"
+          <el-dropdown
+            v-for="menu in filterMenus"
+            :key="menu.key"
+            class="archive-filter-control"
+            trigger="click"
+            placement="bottom-start"
+            popper-class="archive-filter-menu"
+            @command="selectFilterValue(menu.key, $event)"
           >
-            <button class="filter-btn" type="button" @click="toggleFilterDropdown(dropdown.key)">
-              <span>{{ dropdown.label }}</span>
+            <button class="filter-btn archive-filter-trigger" type="button">
+              <span>{{ menu.label }}</span>
               <i class="mdi mdi-chevron-down"></i>
             </button>
-            <div
-              v-if="openFilterKey === dropdown.key"
-              class="archive-dropdown-menu"
-              role="menu"
-              :aria-label="`${dropdown.label}筛选`"
-            >
-              <button
-                v-for="option in dropdown.options"
-                :key="`${dropdown.key}-${option.value}`"
-                type="button"
-                class="archive-dropdown-option"
-                :class="{ active: dropdown.activeValue === option.value }"
-                role="menuitem"
-                @click="selectFilterValue(dropdown.key, option.value)"
-              >
-                {{ option.label }}
-              </button>
-            </div>
-          </div>
+            <template #dropdown>
+              <el-dropdown-menu>
+                <el-dropdown-item
+                  v-for="option in menu.options"
+                  :key="`${menu.key}-${option.value}`"
+                  :command="option.value"
+                  :class="{ 'is-active': menu.activeValue === option.value }"
+                  class="archive-filter-option"
+                  :aria-current="menu.activeValue === option.value ? 'true' : undefined"
+                >
+                  <i v-if="menu.activeValue === option.value" class="mdi mdi-check"></i>
+                  <span>{{ option.label }}</span>
+                </el-dropdown-item>
+              </el-dropdown-menu>
+            </template>
+          </el-dropdown>
         </div>
       </div>