feat: 引入LLM场景路由与后台拓扑管理能力

变更项：

1. 新增 llm.scenes 场景路由层，支持 scene->backend 统一映射，并补充默认场景配置。

2. 扩展 LLMRegistry，新增 scene 解析逻辑；当声明 scene 时强制按场景路由结果生效，保持旧 backend 配置兼容。

3. 扩展后台 /api/system/llm_config 读写能力，支持 scenes 配置保存；新增插件 LLM 依赖扫描与拓扑数据输出。

4. 升级 system_llm 页面：新增场景路由管理区、插件依赖拓扑表，支持可视化查看 插件->scene->backend->provider。

5. 迁移核心插件配置到 scene 模式（保留兼容字段）：dify/global_news/game_task/message_summary/ai_auto_response/member_context/douyu。

6. 调整部分插件初始化默认 llm_config，补充 scene 字段，确保后台场景切换可直接生效。

admin/dashboard/templates/system_llm.html

@@ -42,6 +42,27 @@
             </el-form-item>
         </el-form>
 
+        <el-card class="scene-card" shadow="never">
+            <div slot="header" class="workspace-header">
+                <div>
+                    <h3>场景路由（Scene Binding）</h3>
+                    <p>用业务场景绑定后端。插件优先引用 scene，再由 scene 统一路由到 backend。</p>
+                </div>
+                <el-button size="mini" @click="addScene">新增场景</el-button>
+            </div>
+
+            <div class="scene-list" v-if="llmForm.scenes.length">
+                <div class="scene-row" v-for="(scene, index) in llmForm.scenes" :key="scene.uid">
+                    <el-input v-model="scene.name" placeholder="例如：chat.main"></el-input>
+                    <el-select v-model="scene.backend" placeholder="绑定后端" filterable clearable>
+                        <el-option v-for="item in backendNameOptions" :key="item" :label="item" :value="item"></el-option>
+                    </el-select>
+                    <el-button type="text" class="danger-text" @click="removeScene(index)">删除</el-button>
+                </div>
+            </div>
+            <el-empty v-else description="暂无场景配置，可先新增 chat.main / summary.daily 等"></el-empty>
+        </el-card>
+
         <div class="backend-list" v-if="llmForm.backends.length">
             <el-card
                 v-for="(backend, index) in llmForm.backends"
@@ -132,6 +153,45 @@
         </div>
 
         <el-empty v-else description="暂无后端配置，先新增一个"></el-empty>
+
+        <el-card class="topology-card" shadow="never">
+            <div slot="header" class="workspace-header">
+                <div>
+                    <h3>插件依赖拓扑</h3>
+                    <p>展示 插件 -> scene -> backend -> provider 的实际映射，便于定位切换影响范围。</p>
+                </div>
+            </div>
+            <el-table :data="topologyRows" size="mini" style="width: 100%">
+                <el-table-column prop="plugin" label="插件" min-width="120"></el-table-column>
+                <el-table-column prop="section" label="配置段" min-width="120"></el-table-column>
+                <el-table-column prop="scene" label="Scene" min-width="140">
+                    <template slot-scope="scope">
+                        <el-tag v-if="scope.row.scene" size="mini" :type="scope.row.valid_scene ? 'success' : 'danger'">
+                            {% raw %}{{ scope.row.scene }}{% endraw %}
+                        </el-tag>
+                        <span v-else>-</span>
+                    </template>
+                </el-table-column>
+                <el-table-column prop="backend" label="配置Backend" min-width="160">
+                    <template slot-scope="scope">
+                        <span>{% raw %}{{ scope.row.backend || '-' }}{% endraw %}</span>
+                    </template>
+                </el-table-column>
+                <el-table-column prop="resolved_backend" label="实际Backend" min-width="160">
+                    <template slot-scope="scope">
+                        <el-tag v-if="scope.row.resolved_backend" size="mini" :type="scope.row.valid_backend ? 'success' : 'danger'">
+                            {% raw %}{{ scope.row.resolved_backend }}{% endraw %}
+                        </el-tag>
+                        <span v-else>-</span>
+                    </template>
+                </el-table-column>
+                <el-table-column prop="provider" label="Provider" min-width="120">
+                    <template slot-scope="scope">
+                        <span>{% raw %}{{ scope.row.provider || '-' }}{% endraw %}</span>
+                    </template>
+                </el-table-column>
+            </el-table>
+        </el-card>
     </el-card>
 </div>
 {% endblock %}
@@ -145,9 +205,11 @@
             return {
                 currentView: '17',
                 configPath: '',
+                topologyRows: [],
                 llmForm: {
                     default_backend: '',
-                    backends: []
+                    backends: [],
+                    scenes: []
                 }
             }
         },
@@ -164,6 +226,7 @@
         },
         methods: {
             newBackend() {
+                // 统一后端对象结构，保证新增/编辑时字段完整，避免后端清洗时丢键。
                 return {
                     uid: `${Date.now()}_${Math.random().toString(36).slice(2, 8)}`,
                     name: '',
@@ -185,6 +248,14 @@
                     stream: false
                 };
             },
+            newScene() {
+                // Scene 是“业务场景 -> 后端”的路由单元，插件建议只依赖 scene。
+                return {
+                    uid: `${Date.now()}_${Math.random().toString(36).slice(2, 8)}`,
+                    name: '',
+                    backend: ''
+                };
+            },
             normalizeBackend(item) {
                 return {
                     uid: `${Date.now()}_${Math.random().toString(36).slice(2, 8)}`,
@@ -207,15 +278,36 @@
                     stream: !!item.stream
                 };
             },
+            normalizeScene(item) {
+                return {
+                    uid: `${Date.now()}_${Math.random().toString(36).slice(2, 8)}`,
+                    name: item.name || '',
+                    backend: item.backend || ''
+                };
+            },
             addBackend() {
                 this.llmForm.backends.push(this.newBackend());
             },
+            addScene() {
+                this.llmForm.scenes.push(this.newScene());
+            },
             removeBackend(index) {
                 const removed = this.llmForm.backends[index];
                 this.llmForm.backends.splice(index, 1);
                 if (removed && removed.name && this.llmForm.default_backend === removed.name) {
                     this.llmForm.default_backend = '';
                 }
+                // 后端被删除后，自动清理引用它的 scene，避免保存时出现无效绑定。
+                if (removed && removed.name) {
+                    (this.llmForm.scenes || []).forEach(scene => {
+                        if (scene.backend === removed.name) {
+                            scene.backend = '';
+                        }
+                    });
+                }
+            },
+            removeScene(index) {
+                this.llmForm.scenes.splice(index, 1);
             },
             async loadLlmConfig() {
                 try {
@@ -225,6 +317,8 @@
                         this.configPath = data.config_path || '';
                         this.llmForm.default_backend = data.default_backend || '';
                         this.llmForm.backends = (data.backends || []).map(item => this.normalizeBackend(item));
+                        this.llmForm.scenes = (data.scenes || []).map(item => this.normalizeScene(item));
+                        this.topologyRows = data.topology_rows || [];
                     } else {
                         this.$message.error(response.data.message || '读取全局 LLM 配置失败');
                     }
@@ -239,6 +333,11 @@
                         const cleaned = { ...item };
                         delete cleaned.uid;
                         return cleaned;
+                    }),
+                    scenes: (this.llmForm.scenes || []).map(item => {
+                        const cleaned = { ...item };
+                        delete cleaned.uid;
+                        return cleaned;
                     })
                 };
                 try {
@@ -273,6 +372,14 @@
     .workspace-header p { font-size: 13px; color: #64748b; }
     .config-meta { display: flex; gap: 12px; color: #64748b; font-size: 12px; flex-wrap: wrap; }
     .backend-list { display: flex; flex-direction: column; gap: 16px; }
+    .scene-card, .topology-card { border-radius: 18px; border: 1px solid rgba(148,163,184,0.16); }
+    .scene-list { display: flex; flex-direction: column; gap: 10px; }
+    .scene-row {
+        display: grid;
+        grid-template-columns: minmax(260px, 1fr) minmax(260px, 1fr) auto;
+        gap: 10px;
+        align-items: center;
+    }
     .backend-card { border-radius: 18px; border: 1px solid rgba(148,163,184,0.16); }
     .backend-card-header { display: flex; align-items: center; justify-content: space-between; gap: 12px; }
     .backend-grid {
@@ -286,6 +393,7 @@
         .page-hero { flex-direction: column; align-items: flex-start; }
         .workspace-header { flex-direction: column; align-items: flex-start; }
         .page-hero-actions { flex-wrap: wrap; }
+        .scene-row { grid-template-columns: 1fr; }
         .backend-grid { grid-template-columns: 1fr; }
     }
 </style>