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/blueprints/system.py

@@ -11,6 +11,7 @@ from collections import deque
 import gzip
 import json
 import yaml
+import toml
 from utils.markdown_to_image import get_md2img_health_snapshot, warmup_md2img_browser_sync
 
 # 创建系统信息蓝图
@@ -38,6 +39,113 @@ def _save_system_yaml(config_obj: dict) -> None:
         yaml.safe_dump(config_obj, f, allow_unicode=True, sort_keys=False)
 
 
+def _plugins_root_path() -> str:
+    """返回插件根目录绝对路径。"""
+    return os.path.abspath(os.path.join(os.path.dirname(__file__), '..', '..', '..', 'plugins'))
+
+
+def _scan_plugin_llm_usage() -> list:
+    """扫描各插件 config.toml，提取插件与 LLM 后端/场景的引用关系。
+
+    说明：
+    1. 该扫描仅用于后台可视化，不会改写插件配置；
+    2. 兼容两种写法：顶层 section 下直接写 backend/scene，或嵌套在 llm/api/report_api 等节点；
+    3. 返回结果用于“插件 -> scene -> backend”依赖拓扑展示。
+    """
+    plugins_root = _plugins_root_path()
+    if not os.path.isdir(plugins_root):
+        return []
+
+    usages = []
+
+    def _collect_refs(plugin_name: str, section_name: str, payload: dict) -> None:
+        """从单个配置节点收集 backend/scene 引用。"""
+        if not isinstance(payload, dict):
+            return
+        backend_name = str(payload.get("backend") or "").strip()
+        scene_name = str(payload.get("scene") or payload.get("scene_name") or "").strip()
+        if not backend_name and not scene_name:
+            return
+        usages.append({
+            "plugin": plugin_name,
+            "section": section_name,
+            "backend": backend_name,
+            "scene": scene_name,
+        })
+
+    for item in sorted(os.listdir(plugins_root)):
+        plugin_dir = os.path.join(plugins_root, item)
+        if not os.path.isdir(plugin_dir):
+            continue
+        config_path = os.path.join(plugin_dir, "config.toml")
+        if not os.path.exists(config_path):
+            continue
+        try:
+            config_obj = toml.load(config_path) or {}
+        except Exception as e:
+            logger.warning(f"扫描插件 LLM 依赖失败: plugin={item}, path={config_path}, error={e}")
+            continue
+
+        # 优先扫描每个 section：兼容 [Dify] / [api] / [Douyu.report_api] 等写法。
+        for section_name, section_value in config_obj.items():
+            if isinstance(section_value, dict):
+                _collect_refs(item, str(section_name), section_value)
+                # 二层兜底：处理 llm/api/report_api 等嵌套节点。
+                for nested_name, nested_value in section_value.items():
+                    if isinstance(nested_value, dict):
+                        _collect_refs(item, f"{section_name}.{nested_name}", nested_value)
+        # 顶层兜底：兼容极少数直接写在根节点的 backend/scene。
+        _collect_refs(item, "__root__", config_obj if isinstance(config_obj, dict) else {})
+
+    # 去重：同插件同 section 仅保留一条记录，避免前后兜底重复。
+    unique = {}
+    for row in usages:
+        key = f"{row.get('plugin')}::{row.get('section')}::{row.get('scene')}::{row.get('backend')}"
+        unique[key] = row
+    return sorted(unique.values(), key=lambda x: (x.get("plugin", ""), x.get("section", "")))
+
+
+def _build_llm_topology() -> dict:
+    """构建 LLM 拓扑视图（供后台页面直观展示依赖关系）。"""
+    config_obj = _load_system_yaml()
+    llm_config = config_obj.get("llm", {}) or {}
+    scenes = llm_config.get("scenes", {}) or {}
+    backends = llm_config.get("backends", {}) or {}
+    default_backend = str(llm_config.get("default_backend", "") or "").strip()
+
+    plugin_usages = _scan_plugin_llm_usage()
+    topology_rows = []
+    for usage in plugin_usages:
+        scene_name = str(usage.get("scene") or "").strip()
+        backend_name = str(usage.get("backend") or "").strip()
+        resolved_backend = backend_name
+        # 若插件只写了 scene，则由 scenes 路由解析后端。
+        if not resolved_backend and scene_name:
+            resolved_backend = str(scenes.get(scene_name) or "").strip()
+        # 若既没有 scene 也没有 backend，则兜底 default_backend（仅展示，不改配置）。
+        if not resolved_backend:
+            resolved_backend = default_backend
+
+        topology_rows.append({
+            "plugin": usage.get("plugin", ""),
+            "section": usage.get("section", ""),
+            "scene": scene_name,
+            "backend": backend_name,
+            "resolved_backend": resolved_backend,
+            "provider": str((backends.get(resolved_backend) or {}).get("provider", "") or "").strip(),
+            "valid_scene": bool((not scene_name) or scene_name in scenes),
+            "valid_backend": bool((not resolved_backend) or resolved_backend in backends),
+        })
+
+    return {
+        "default_backend": default_backend,
+        "scenes": scenes if isinstance(scenes, dict) else {},
+        "backends": backends if isinstance(backends, dict) else {},
+        "plugin_usages": plugin_usages,
+        "topology_rows": topology_rows,
+    }
+
+
 @system_bp.route('/api_docs')
 @login_required
 def api_docs():
@@ -235,6 +343,7 @@ def get_system_llm_config():
         config_obj = _load_system_yaml()
         llm_config = config_obj.get("llm", {}) or {}
         backends = llm_config.get("backends", {}) or {}
+        scenes = llm_config.get("scenes", {}) or {}
         backend_list = []
         for name, backend in backends.items():
             if not isinstance(backend, dict):
@@ -243,11 +352,29 @@ def get_system_llm_config():
             item["name"] = name
             backend_list.append(item)
         backend_list.sort(key=lambda item: item.get("name", ""))
+
+        scene_list = []
+        if isinstance(scenes, dict):
+            for scene_name, backend_name in scenes.items():
+                scene_name = str(scene_name or "").strip()
+                backend_name = str(backend_name or "").strip()
+                if not scene_name:
+                    continue
+                scene_list.append({
+                    "name": scene_name,
+                    "backend": backend_name,
+                })
+        scene_list.sort(key=lambda item: item.get("name", ""))
+
+        topology = _build_llm_topology()
         return jsonify({
             "success": True,
             "data": {
                 "default_backend": llm_config.get("default_backend", ""),
                 "backends": backend_list,
+                "scenes": scene_list,
+                "topology_rows": topology.get("topology_rows", []),
+                "plugin_usages": topology.get("plugin_usages", []),
                 "config_path": _system_config_path(),
             }
         })
@@ -264,8 +391,11 @@ def update_system_llm_config():
         data = request.get_json() or {}
         default_backend = str(data.get("default_backend") or "").strip()
         backend_list = data.get("backends", []) or []
+        scene_list = data.get("scenes", []) or []
         if not isinstance(backend_list, list):
             return jsonify({"success": False, "message": "backends 格式不正确"}), 400
+        if not isinstance(scene_list, list):
+            return jsonify({"success": False, "message": "scenes 格式不正确"}), 400
 
         normalized_backends = {}
         for raw in backend_list:
@@ -290,10 +420,24 @@ def update_system_llm_config():
         if default_backend and default_backend not in normalized_backends:
             return jsonify({"success": False, "message": "默认后端不存在"}), 400
 
+        normalized_scenes = {}
+        for raw in scene_list:
+            if not isinstance(raw, dict):
+                continue
+            scene_name = str(raw.get("name") or "").strip()
+            backend_name = str(raw.get("backend") or "").strip()
+            if not scene_name:
+                continue
+            if backend_name and backend_name not in normalized_backends:
+                return jsonify({"success": False, "message": f"场景 {scene_name} 绑定的后端不存在"}), 400
+            # 允许场景先占位但暂不绑定后端，方便后台分步配置。
+            normalized_scenes[scene_name] = backend_name
+
         config_obj = _load_system_yaml()
         config_obj["llm"] = {
             "default_backend": default_backend,
             "backends": normalized_backends,
+            "scenes": normalized_scenes,
         }
         _save_system_yaml(config_obj)