feat: 实现自建情景功能

## 功能概述
- 用户可创建、编辑、删除自定义情景
- 支持自定义情景名称、图标、描述、Prompt、首句引导
- 完整的权限隔离，用户只能管理自己的情景
- 深度集成 Eino 框架，动态加载自建情景 Prompt

## 后端实现
### 数据库
- 新增 user_scenarios 表
- 支持用户配额（最多 20 个）
- 字段验证：description 可选，prompt 最小 10 字符

### API
- GET /api/scenarios - 获取用户情景列表
- POST /api/scenarios - 创建情景
- GET /api/scenarios/:id - 获取详情
- PATCH /api/scenarios/:id - 更新情景
- DELETE /api/scenarios/:id - 删除情景

### Eino 集成
- PipelineState 添加 UserID 字段
- nodes_history 动态加载用户自建情景
- GetScenarioPrompt 支持自建情景优先级

## 前端实现
### 组件
- CreateScenarioModal - 创建情景对话框
- EditScenarioModal - 编辑情景对话框
- ConfigPanel 改造 - 分组显示系统预置和自建情景

### Hook
- useScenarios - 合并系统和自建情景，提供 CRUD 接口

### 国际化
- 中文、英文、日文翻译支持

## 问题修复
- 修复 CORS 问题：使用 Vite 代理
- 统一验证规则：description 可选，prompt 最小 10 字符
- 修复数据库约束：使用 NULLIF 处理空字符串

## 文件变更
新增文件: 13 个
修改文件: 14 个

详见文档: docs/自建情景功能完整文档.md

frontend/src/lib/api/scenarios.ts

@@ -0,0 +1,120 @@
+// ============================================================
+// scenarios API — 用户自建情景 API 调用
+// 职责：封装 /api/scenarios 的 CRUD 操作
+// ============================================================
+
+// 开发环境通过 Vite 代理，生产环境使用同域名
+const API_BASE = "";
+
+export interface UserScenario {
+  id: string;
+  user_id: string;
+  name: string;
+  icon: string;
+  description: string;
+  prompt: string;
+  greeting: string;
+  language: string;
+  created_at: string;
+  updated_at: string;
+}
+
+export interface CreateScenarioRequest {
+  name: string;
+  icon?: string;
+  description?: string;
+  prompt: string;
+  greeting?: string;
+  language?: string;
+}
+
+export interface UpdateScenarioRequest {
+  name?: string;
+  icon?: string;
+  description?: string;
+  prompt?: string;
+  greeting?: string;
+  language?: string;
+}
+
+export interface ScenariosListResponse {
+  scenarios: UserScenario[];
+  total: number;
+}
+
+// 获取用户的所有自建情景
+export async function listUserScenarios(token: string): Promise<ScenariosListResponse> {
+  const res = await fetch(`${API_BASE}/api/scenarios`, {
+    headers: { Authorization: `Bearer ${token}` },
+  });
+  if (!res.ok) {
+    const err = await res.json().catch(() => ({ error: "Network error" }));
+    throw new Error(err.error || "Failed to list scenarios");
+  }
+  return res.json();
+}
+
+// 创建新情景
+export async function createUserScenario(
+  token: string,
+  data: CreateScenarioRequest
+): Promise<UserScenario> {
+  const res = await fetch(`${API_BASE}/api/scenarios`, {
+    method: "POST",
+    headers: {
+      "Content-Type": "application/json",
+      Authorization: `Bearer ${token}`,
+    },
+    body: JSON.stringify(data),
+  });
+  if (!res.ok) {
+    const err = await res.json().catch(() => ({ error: "Network error" }));
+    throw new Error(err.error || "Failed to create scenario");
+  }
+  return res.json();
+}
+
+// 获取单个情景详情
+export async function getUserScenario(token: string, id: string): Promise<UserScenario> {
+  const res = await fetch(`${API_BASE}/api/scenarios/${id}`, {
+    headers: { Authorization: `Bearer ${token}` },
+  });
+  if (!res.ok) {
+    const err = await res.json().catch(() => ({ error: "Network error" }));
+    throw new Error(err.error || "Failed to get scenario");
+  }
+  return res.json();
+}
+
+// 更新情景
+export async function updateUserScenario(
+  token: string,
+  id: string,
+  data: UpdateScenarioRequest
+): Promise<UserScenario> {
+  const res = await fetch(`${API_BASE}/api/scenarios/${id}`, {
+    method: "PATCH",
+    headers: {
+      "Content-Type": "application/json",
+      Authorization: `Bearer ${token}`,
+    },
+    body: JSON.stringify(data),
+  });
+  if (!res.ok) {
+    const err = await res.json().catch(() => ({ error: "Network error" }));
+    throw new Error(err.error || "Failed to update scenario");
+  }
+  return res.json();
+}
+
+// 删除情景
+export async function deleteUserScenario(token: string, id: string): Promise<void> {
+  const res = await fetch(`${API_BASE}/api/scenarios/${id}`, {
+    method: "DELETE",
+    headers: { Authorization: `Bearer ${token}` },
+  });
+  if (!res.ok) {
+    const err = await res.json().catch(() => ({ error: "Network error" }));
+    throw new Error(err.error || "Failed to delete scenario");
+  }
+}

frontend/src/lib/i18n/en-US.ts

@@ -178,4 +178,41 @@ export const enUS: TranslationMap = {
   // Account (in settings)
   "settings.account": "Account",
   "settings.account.user": "Current user",
+
+  // Custom scenarios
+  "settings.scenario.system": "System Scenarios",
+  "settings.scenario.custom": "My Scenarios",
+  "settings.scenario.empty": "No custom scenarios yet. Click the button above to create one.",
+  "scenario.create.button": "New Scenario",
+  "scenario.create.title": "Create Custom Scenario",
+  "scenario.edit.title": "Edit Scenario",
+  "scenario.create.name": "Scenario Name",
+  "scenario.create.namePlaceholder": "e.g. Creative Writing Coach",
+  "scenario.create.icon": "Icon",
+  "scenario.create.description": "Brief Description",
+  "scenario.create.descriptionPlaceholder": "One-line summary of this scenario",
+  "scenario.create.prompt": "System Prompt",
+  "scenario.create.promptPlaceholder": "Define the AI's role and interaction rules...",
+  "scenario.create.promptGuide": "View Guide",
+  "scenario.create.promptGuide.tips": "Writing tips:",
+  "scenario.create.promptGuide.tip1": "Clearly define the role: who you are, who you are not",
+  "scenario.create.promptGuide.tip2": "List interaction rules: how to respond, how many sentences",
+  "scenario.create.promptGuide.tip3": "Add constraints: what not to do",
+  "scenario.create.promptGuide.example": "Example:",
+  "scenario.create.greeting": "Greeting (Optional)",
+  "scenario.create.greetingPlaceholder": "The first message when switching to this scenario...",
+  "scenario.create.language": "Default Language",
+  "scenario.error.nameLength": "Scenario name must be 2-50 characters",
+  "scenario.error.promptLength": "Prompt must be 10-2000 characters",
+  "scenario.error.greetingLength": "Greeting must not exceed 500 characters",
+
+  // Common actions
+  "common.cancel": "Cancel",
+  "common.create": "Create",
+  "common.creating": "Creating...",
+  "common.save": "Save",
+  "common.saving": "Saving...",
+  "common.edit": "Edit",
+  "common.delete": "Delete",
+  "common.confirmDelete": "Click again to confirm",
 };

frontend/src/lib/i18n/ja-JP.ts

@@ -178,4 +178,41 @@ export const jaJP: TranslationMap = {
   // Account (in settings)
   "settings.account": "アカウント",
   "settings.account.user": "現在のユーザー",
+
+  // Custom scenarios
+  "settings.scenario.system": "システムシナリオ",
+  "settings.scenario.custom": "マイシナリオ",
+  "settings.scenario.empty": "カスタムシナリオはまだありません。上のボタンをクリックして作成してください。",
+  "scenario.create.button": "新しいシナリオ",
+  "scenario.create.title": "カスタムシナリオを作成",
+  "scenario.edit.title": "シナリオを編集",
+  "scenario.create.name": "シナリオ名",
+  "scenario.create.namePlaceholder": "例：クリエイティブライティングコーチ",
+  "scenario.create.icon": "アイコン",
+  "scenario.create.description": "簡単な説明",
+  "scenario.create.descriptionPlaceholder": "このシナリオの概要を一文で",
+  "scenario.create.prompt": "システムプロンプト",
+  "scenario.create.promptPlaceholder": "AIの役割と対話ルールを定義...",
+  "scenario.create.promptGuide": "ガイドを見る",
+  "scenario.create.promptGuide.tips": "作成のヒント：",
+  "scenario.create.promptGuide.tip1": "役割を明確に定義：何者で、何者でないか",
+  "scenario.create.promptGuide.tip2": "対話ルールをリスト化：応答方法、文数",
+  "scenario.create.promptGuide.tip3": "制約を追加：何をしないか",
+  "scenario.create.promptGuide.example": "例：",
+  "scenario.create.greeting": "挨拶（オプション）",
+  "scenario.create.greetingPlaceholder": "このシナリオに切り替えた時の最初のメッセージ...",
+  "scenario.create.language": "デフォルト言語",
+  "scenario.error.nameLength": "シナリオ名は2〜50文字で入力してください",
+  "scenario.error.promptLength": "プロンプトは10〜2000文字で入力してください",
+  "scenario.error.greetingLength": "挨拶は500文字以内で入力してください",
+
+  // Common actions
+  "common.cancel": "キャンセル",
+  "common.create": "作成",
+  "common.creating": "作成中...",
+  "common.save": "保存",
+  "common.saving": "保存中...",
+  "common.edit": "編集",
+  "common.delete": "削除",
+  "common.confirmDelete": "もう一度クリックして確認",
 };

frontend/src/lib/i18n/zh-CN.ts

@@ -178,4 +178,41 @@ export const zhCN: TranslationMap = {
   // Account (in settings)
   "settings.account": "账号",
   "settings.account.user": "当前用户",
+
+  // Custom scenarios
+  "settings.scenario.system": "系统预置情景",
+  "settings.scenario.custom": "我的情景",
+  "settings.scenario.empty": "还没有自建情景，点击上方按钮创建",
+  "scenario.create.button": "创建新情景",
+  "scenario.create.title": "创建自建情景",
+  "scenario.edit.title": "编辑情景",
+  "scenario.create.name": "情景名称",
+  "scenario.create.namePlaceholder": "例如：创意写作导师",
+  "scenario.create.icon": "图标",
+  "scenario.create.description": "简短描述",
+  "scenario.create.descriptionPlaceholder": "一句话介绍这个情景的作用",
+  "scenario.create.prompt": "System Prompt",
+  "scenario.create.promptPlaceholder": "定义 AI 的角色和交互规则...",
+  "scenario.create.promptGuide": "查看编写指南",
+  "scenario.create.promptGuide.tips": "编写提示：",
+  "scenario.create.promptGuide.tip1": "明确角色定位：你是谁，不是谁",
+  "scenario.create.promptGuide.tip2": "列出交互规则：如何回答，每次几句话",
+  "scenario.create.promptGuide.tip3": "添加约束条件：不要做什么",
+  "scenario.create.promptGuide.example": "示例：",
+  "scenario.create.greeting": "首句引导（可选）",
+  "scenario.create.greetingPlaceholder": "切换到此情景时，AI 的第一句话...",
+  "scenario.create.language": "默认语言",
+  "scenario.error.nameLength": "情景名称需要 2-50 个字符",
+  "scenario.error.promptLength": "Prompt 需要 10-2000 个字符",
+  "scenario.error.greetingLength": "首句引导不超过 500 个字符",
+
+  // Common actions
+  "common.cancel": "取消",
+  "common.create": "创建",
+  "common.creating": "创建中...",
+  "common.save": "保存",
+  "common.saving": "保存中...",
+  "common.edit": "编辑",
+  "common.delete": "删除",
+  "common.confirmDelete": "再次点击确认删除",
 };