feat(core): standalone image-gen endpoint + api.ts methods (profile/password/avatar/generate-image)

- POST /api/ai/generate-image/ — project-less image generation (AITask.project nullable, no schema change),
  reuses VolcanoArk image_generation + credit reserve/charge; modes image/model/cover.
  Verified: manage.py check clean; 2 active IMAGE models present (doubao-seedream-4.5/5.0).
  (Real generation calls Volcano API + charges credit — not yet live-tested to avoid spend.)
- api.ts: updateProfile / changePassword / uploadAvatar / generateImage

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

core/backend/apps/ai/views.py

@@ -1,9 +1,36 @@
+from rest_framework import status
+from rest_framework.response import Response
+from rest_framework.views import APIView
 from rest_framework.viewsets import ReadOnlyModelViewSet
 
-from apps.common.api import TeamScopedViewSetMixin
+from apps.assets.serializers import AssetSerializer
+from apps.common.api import TeamScopedViewSetMixin, get_current_team
 
 from .models import AITask, ModelConfig
 from .serializers import AITaskSerializer, ModelConfigSerializer
+from .services import generate_standalone_image
+
+
+class GenerateImageView(APIView):
+    """POST /api/ai/generate-image/ — 独立生图(不绑项目)· 图片创作/模特图/平台套图共用。"""
+
+    def post(self, request):
+        prompt = str(request.data.get("prompt") or "").strip()
+        if not prompt:
+            return Response({"detail": "prompt 不能为空"}, status=status.HTTP_400_BAD_REQUEST)
+        mode = str(request.data.get("mode") or "image")
+        try:
+            count = int(request.data.get("count") or 1)
+        except (TypeError, ValueError):
+            count = 1
+        team = get_current_team(request.user)
+        try:
+            assets = generate_standalone_image(team=team, user=request.user, prompt=prompt, mode=mode, count=count)
+        except ValueError as exc:
+            return Response({"detail": str(exc)}, status=status.HTTP_400_BAD_REQUEST)
+        except Exception as exc:  # noqa: BLE001 — 生成失败已回滚额度,返回明确错误给前端
+            return Response({"detail": f"生成失败: {exc}"}, status=status.HTTP_502_BAD_GATEWAY)
+        return Response({"assets": AssetSerializer(assets, many=True).data}, status=status.HTTP_201_CREATED)
 
 
 class AITaskViewSet(TeamScopedViewSetMixin, ReadOnlyModelViewSet):