Refactor AI config to step-based wizard with DeepSeek defaults

apps/server/src/ai-config/dto/ai-config.dto.ts

@@ -24,8 +24,8 @@ export class SaveAiConfigDto {
   @IsIn(PROVIDERS)
   provider!: AiProvider;
 
-  @ValidateIf((o: SaveAiConfigDto) => o.provider === AiProvider.OPENAI_COMPATIBLE || o.baseUrl !== undefined)
-  @IsNotEmpty({ message: 'OPENAI_COMPATIBLE 模式必须提供 baseUrl' })
+  @ValidateIf((o: SaveAiConfigDto) => o.provider === AiProvider.OPENAI_COMPATIBLE || (o.baseUrl !== undefined && o.baseUrl !== ''))
+  @IsNotEmpty({ message: 'Base URL 不能为空' })
   @IsString()
   baseUrl?: string;
 
@@ -113,4 +113,32 @@ export interface AiRuntimeConfig {
   enabled: boolean;
 }
 
+/** DTO for POST /api/ai/config/models — fetch available model list from provider */
+export class FetchModelsDto {
+  @IsOptional()
+  @IsIn(PROVIDERS)
+  provider?: AiProvider;
+
+  @IsOptional()
+  @IsString()
+  baseUrl?: string;
+
+  @IsOptional()
+  @IsString()
+  apiKey?: string;
+
+  @IsOptional()
+  @IsInt()
+  @Min(1000)
+  @Max(120000)
+  timeoutMs?: number;
+}
+
+/** Response shape for POST /api/ai/config/models */
+export interface FetchModelsResultDto {
+  success: boolean;
+  models: Array<{ id: string }>;
+  message?: string;
+}
+
 export { DEFAULT_BASE_URLS };