feat(B3): 站点编辑弹窗增自定义样式面板(config_json.custom_css)

- 折叠面板 textarea(等宽字体/10240计数/示例提示),面板为唯一编辑入口
- custom_css 入 RESERVED_SITE_CONFIG_KEYS(结构化表单保留键,不与扩展行重复编辑)
- vitest 25/25 绿(新增保留键往返用例)+build 成功

src/views/cms/SiteManage.vue

@@ -131,6 +131,9 @@ const form = reactive({
 const editThemeParams = ref<FormModelValue>({});
 const editTheme = computed(() => themeMeta.value[form.theme]);
 
+/** B3 自定义样式（config_json.custom_css）：面板为唯一编辑入口，SiteConfigForm 侧该键为保留键 */
+const customCss = ref("");
+
 /** 编辑内预览 */
 const previewVisible = ref(false);
 
@@ -192,11 +195,35 @@ function openEdit(row: SiteVo) {
         configJson: row.configJson || "",
         status: row.status,
     });
+    customCss.value = readCustomCss(form.configJson);
     const t = editTheme.value;
     editThemeParams.value = t ? themeParamsFromConfigJson(row.configJson, t) : {};
     modalVisible.value = true;
 }
 
+function readCustomCss(configJson: string): string {
+    try {
+        const obj = configJson && configJson.trim() ? JSON.parse(configJson) : {};
+        return obj && typeof obj === "object" && typeof obj.custom_css === "string" ? obj.custom_css : "";
+    } catch {
+        return "";
+    }
+}
+
+/** 把面板值写入/移出 configJson（空值移除键；与 SiteConfigForm 的 preserved 往返兼容） */
+function withCustomCss(configJson: string, css: string): string {
+    let obj: Record<string, unknown>;
+    try {
+        obj = configJson && configJson.trim() ? JSON.parse(configJson) : {};
+        if (!obj || typeof obj !== "object" || Array.isArray(obj)) obj = {};
+    } catch {
+        obj = {};
+    }
+    if (css.trim()) obj.custom_css = css;
+    else delete obj.custom_css;
+    return JSON.stringify(obj);
+}
+
 function pickTheme(name: string) {
     if (form.theme === name) return;
     form.theme = name;
@@ -213,6 +240,7 @@ async function save() {
     try {
         const t = editTheme.value;
         const themeParams = t ? editThemeParams.value : {};
+        const baseConfig = withCustomCss(form.configJson || "", customCss.value);
         await siteApi
             .save({
                 id: form.id,
@@ -223,7 +251,7 @@ async function save() {
                 schName: isSchoolAdmin.value ? undefined : form.schName || undefined,
                 name: form.name,
                 theme: form.theme || undefined,
-                configJson: t ? mergeThemeParamsIntoConfigJson(form.configJson || "", t, themeParams) : form.configJson || undefined,
+                configJson: t ? mergeThemeParamsIntoConfigJson(baseConfig, t, themeParams) : baseConfig || undefined,
                 status: form.status,
             })
             .send();
@@ -332,6 +360,23 @@ watch(() => store.currentSchool?.schId, () => run());
                     </RadioGroup>
                 </FormItem>
             </Form>
+            <!-- B3 自定义样式（config_json.custom_css，服务端黑名单强校验） -->
+            <Collapse class="css-collapse">
+                <Panel name="css" header="自定义样式（站点级 CSS 覆盖）">
+                    <Input
+                        v-model="customCss"
+                        type="textarea"
+                        :rows="6"
+                        :maxlength="10240"
+                        placeholder="如：--primary:#59aeeb;  或  .site-header{height:80px}"
+                        class="css-editor"
+                    />
+                    <div class="css-meta">
+                        <span>{{ customCss.length }}/10240 字符</span>
+                        <span>保存后门户立即生效（缓存自动失效）；服务端将拒绝 &lt;/style、&lt;script、@import、expression( 等危险内容</span>
+                    </div>
+                </Panel>
+            </Collapse>
             <!-- 站点配置结构化表单（独立 Form 分区，v-model 直绑 configJson） -->
             <SiteConfigForm ref="configFormRef" v-model="form.configJson" />
             <template #footer>
@@ -360,4 +405,20 @@ watch(() => store.currentSchool?.schId, () => run());
 .preview-btn {
     margin: 8px 0 0;
 }
+.css-collapse {
+    margin: 4px 0 12px;
+    .css-editor :deep(textarea) {
+        font-family: Consolas, Monaco, monospace;
+        font-size: 12px;
+    }
+    .css-meta {
+        display: flex;
+        justify-content: space-between;
+        gap: 12px;
+        margin-top: 6px;
+        color: #999;
+        font-size: 12px;
+        line-height: 1.6;
+    }
+}
 </style>