refactor(db): 统一数据库 schema — 软删除、命名规范、约束标准化

- 全表新增 deleted_at 列，统一软删除替代硬删除+archived_at
- models.model_id 重命名为 external_id，消除语义混淆
- conversations.model_id 改为可空（模型为建议而非绑定）
- messages 新增 updated_at，移除 CASCADE 改为 DAO 层级联
- 移除 DB 层 UNIQUE 约束，改为应用层检查（配合软删除）
- 新增 helpers.ts（baseColumns + 构造层防御）、ESLint 规则、契约测试
- 迁移 0004 补全 CHECK 约束（providers.type/materials.status/messages.role）
- DAO 层全面重写：级联软删除、应用层唯一、provider 删除保护
- 路由/前端/测试全量适配 externalId 重命名及类型变更

src/shared/api.ts

@@ -6,7 +6,7 @@ export interface ApiErrorResponse {
 export interface Conversation {
   createdAt: string;
   id: string;
-  modelId: string;
+  modelId: null | string;
   projectId: string;
   title: string;
   updatedAt: string;
@@ -36,8 +36,8 @@ export interface CreateMaterialRequest {
 export interface CreateModelRequest {
   capabilities: ModelCapability[];
   contextLength?: null | number;
+  externalId: string;
   maxOutputTokens?: null | number;
-  modelId: string;
   name: string;
   providerId: string;
 }
@@ -94,6 +94,7 @@ export interface Message {
   id: string;
   parts: null | string;
   role: "assistant" | "system" | "user";
+  updatedAt: string;
 }
 
 export interface MessageListResponse {
@@ -114,9 +115,9 @@ export interface Model {
   capabilities: ModelCapability[];
   contextLength: null | number;
   createdAt: string;
+  externalId: string;
   id: string;
   maxOutputTokens: null | number;
-  modelId: string;
   name: string;
   providerId: string;
   updatedAt: string;
@@ -171,7 +172,6 @@ export interface ModelTestResultResponse {
 }
 
 export interface Project {
-  archivedAt: null | string;
   createdAt: string;
   description: string;
   id: string;
@@ -238,15 +238,15 @@ export type ProviderType = "anthropic" | "openai" | "openai-compatible";
 export type RuntimeMode = "development" | "production" | "test";
 
 export interface TestModelRequest {
-  modelId: string;
+  externalId: string;
   providerId: string;
 }
 
 export interface UpdateModelRequest {
   capabilities?: ModelCapability[];
   contextLength?: null | number;
+  externalId?: string;
   maxOutputTokens?: null | number;
-  modelId?: string;
   name?: string;
   providerId?: string;
 }