feat: добавить endpoint picture/srcset

- добавлен contract DTO для picture sources и fallback image
- реализована выдача versioned Gateway URLs по static presets
- обновлена документация business API и dev smoke flow

apps/backend/src/assets/assets.controller.ts

@@ -12,6 +12,7 @@ import {
 } from "@nestjs/swagger"
 
 import { AssetsService } from "./assets.service"
+import { AssetPictureResponseDto } from "./asset-picture-response.dto"
 import { AssetResponseDto, AssetVariantsResponseDto, AssetsListResponseDto } from "./asset-response.dto"
 import { CreateAssetVersionRequestDto, CreateAssetVersionResponseDto } from "./create-asset-version.dto"
 import { CreateAssetVariantsRequestDto, CreateAssetVariantsResponseDto } from "./create-asset-variants.dto"
@@ -77,6 +78,30 @@ export class AssetsController {
     return this.assets.createAssetVersion(publicId, request)
   }
 
+  @Get(":publicId/picture")
+  @ApiOperation({
+    summary: "получить picture/srcset URLs",
+    description:
+      "Возвращает готовый контракт для `<picture>` и `<img>` по static preset: sources, srcset, fallback src, sizes и versioned Gateway URLs. Endpoint не ставит generation jobs: Gateway сгенерирует bytes lazy или отдаст cache.",
+  })
+  @ApiParam({ description: "Публичный идентификатор asset.", example: "asset_demo", name: "publicId" })
+  @ApiQuery({ description: "Static preset для picture contract.", example: "card", name: "preset", required: true })
+  @ApiQuery({ description: "Версия source image. Если не передана, используется currentVersion asset.", example: 1, name: "version", required: false })
+  @ApiQuery({ description: "Quality. Если не передано, берётся default quality preset.", example: 80, name: "quality", required: false })
+  @ApiQuery({ description: "Значение для HTML `sizes`.", example: "(min-width: 768px) 50vw, 100vw", name: "sizes", required: false })
+  @ApiOkResponse({ description: "Picture/srcset contract возвращён.", type: AssetPictureResponseDto })
+  @ApiBadRequestResponse({ description: "Некорректный preset, version, quality или sizes." })
+  @ApiNotFoundResponse({ description: "Asset или version не найдены." })
+  getAssetPicture(
+    @Param("publicId") publicId: string,
+    @Query("preset") preset?: string,
+    @Query("version") version?: string,
+    @Query("quality") quality?: string,
+    @Query("sizes") sizes?: string,
+  ): Promise<AssetPictureResponseDto> {
+    return this.assets.getAssetPicture(publicId, { preset, quality, sizes, version })
+  }
+
   @Get(":publicId/variants")
   @ApiOperation({
     summary: "получить variants asset",