feat(multimodal): 实现本地模型管线与请求用量配置

backend/app/provider_preview_routes.py

@@ -0,0 +1,43 @@
+from fastapi import APIRouter
+from pydantic import BaseModel
+from app.contracts import ProviderCreateRequest, ProviderConfig, ModelRequest, Message, MessageRole
+from app.providers.factory import ProviderFactory
+from app.request_overrides import apply_overrides
+
+router = APIRouter(prefix="/api/providers", tags=["Providers"])
+
+
+class PreviewRequest(BaseModel):
+    provider: ProviderCreateRequest
+    stream: bool = True
+    capability: str = "chat"
+
+
+@router.post("/request-preview")
+async def preview(request: PreviewRequest):
+    class NoCredentials:
+        def resolve(self, key):
+            return None
+    config = ProviderConfig(provider_id="preview", **request.provider.model_dump())
+    if request.capability != "chat":
+        from app.errors import ApiError
+        if request.capability not in {"embedding", "transcription", "speaker_matching"}:
+            raise ApiError(422, "INVALID_CAPABILITY", "Unknown capability.")
+        payload = {"model": config.default_model or "<模型 ID>"}
+        payload["input" if request.capability == "embedding" else "file"] = "<运行时输入，不包含正文或文件>"
+        if request.capability == "speaker_matching":
+            payload["reference_file"] = "<声纹参考附件>"
+    else:
+        from app.providers.factory import UnsupportedProviderError
+        from app.errors import ApiError
+        try:
+            adapter = ProviderFactory(NoCredentials()).build(config)
+        except UnsupportedProviderError as exc:
+            raise ApiError(422, "PROVIDER_TYPE_UNSUPPORTED", "该协议不支持请求预览。") from exc
+        model_request = ModelRequest(provider_id="preview", model=config.default_model or "<模型 ID>",
+            messages=[Message(role=MessageRole.user, content="<运行时消息，已隐藏>")])
+        build = getattr(adapter, "_payload", None) or adapter._chat_payload
+        payload = build(model_request, stream=request.stream)
+    return {"body": apply_overrides(payload, config.request_overrides, request.capability,
+                                    stream=request.stream if request.capability == "chat" else False),
+            "contains_credentials": False, "execution": "preview_only"}