refactor: 项目结构优化与FastAPI生命周期更新

重构项目目录结构，提高代码组织性和可维护性

将schemas目录重命名为domain，更好地表达领域模型概念
将services目录细分为service/chat、service/image等子目录
将api目录重命名为router，更符合FastAPI惯例
创建utils目录存放通用工具函数
更新FastAPI应用程序生命周期管理

替换已弃用的on_event方法为推荐的lifespan事件处理器
添加应用程序关闭时的日志记录
代码质量改进

抽取常量到constants.py，减少硬编码值
添加helpers.py提供通用工具函数
优化配置管理，使用环境变量和默认值
完善文档字符串，提高代码可读性

app/domain/gemini_models.py

@@ -0,0 +1,40 @@
+from typing import List, Optional, Dict, Any, Literal
+from pydantic import BaseModel
+
+
+class SafetySetting(BaseModel):
+    category: Optional[Literal["HARM_CATEGORY_HATE_SPEECH", "HARM_CATEGORY_DANGEROUS_CONTENT", "HARM_CATEGORY_HARASSMENT", "HARM_CATEGORY_SEXUALLY_EXPLICIT", "HARM_CATEGORY_CIVIC_INTEGRITY"]] = None
+    threshold: Optional[Literal["HARM_BLOCK_THRESHOLD_UNSPECIFIED", "BLOCK_LOW_AND_ABOVE", "BLOCK_MEDIUM_AND_ABOVE", "BLOCK_ONLY_HIGH", "BLOCK_NONE", "OFF"]] = None
+
+
+class GenerationConfig(BaseModel):
+    stopSequences: Optional[List[str]] = None
+    responseMimeType: Optional[str] = None
+    responseSchema: Optional[Dict[str, Any]] = None
+    candidateCount: Optional[int] = 1
+    maxOutputTokens: Optional[int] = None
+    temperature: Optional[float] = None
+    topP: Optional[float] = None
+    topK: Optional[int] = None
+    presencePenalty: Optional[float] = None
+    frequencyPenalty: Optional[float] = None
+    responseLogprobs: Optional[bool] = None
+    logprobs: Optional[int] = None
+
+
+class SystemInstruction(BaseModel):
+    role: str = "system"
+    parts: List[Dict[str, Any]]
+
+
+class GeminiContent(BaseModel):
+    role: str
+    parts: List[Dict[str, Any]]
+
+
+class GeminiRequest(BaseModel):
+    contents: List[GeminiContent] = []
+    tools: Optional[List[Dict[str, Any]]] = []
+    safetySettings: Optional[List[SafetySetting]] = None
+    generationConfig: Optional[GenerationConfig] = None
+    systemInstruction: Optional[SystemInstruction] = None

app/domain/image_models.py

@@ -0,0 +1,23 @@
+class ImageMetadata:
+    def __init__(self, width: int, height: int, filename: str, size: int, url: str, delete_url: str | None = None):
+        self.width = width
+        self.height = height
+        self.filename = filename
+        self.size = size
+        self.url = url
+        self.delete_url = delete_url
+    
+    
+class UploadResponse:
+    def __init__(self, success: bool, code: str, message: str, data: ImageMetadata):
+        self.success = success
+        self.code = code
+        self.message = message
+        self.data = data
+    
+    
+class ImageUploader:
+    def upload(self, file: bytes, filename: str) -> UploadResponse:
+        raise NotImplementedError
+    
+    

app/domain/openai_models.py

@@ -0,0 +1,32 @@
+from pydantic import BaseModel
+from typing import List, Optional, Union
+
+from app.core.constants import DEFAULT_MAX_TOKENS, DEFAULT_MODEL, DEFAULT_TEMPERATURE, DEFAULT_TOP_K, DEFAULT_TOP_P
+
+
+class ChatRequest(BaseModel):
+    messages: List[dict]
+    model: str = DEFAULT_MODEL
+    temperature: Optional[float] = DEFAULT_TEMPERATURE
+    stream: Optional[bool] = False
+    tools: Optional[List[dict]] = []
+    max_tokens: Optional[int] = DEFAULT_MAX_TOKENS
+    top_p: Optional[float] = DEFAULT_TOP_P
+    top_k: Optional[int] = DEFAULT_TOP_K
+    stop: Optional[List[str]] = []
+
+
+class EmbeddingRequest(BaseModel):
+    input: Union[str, List[str]]
+    model: str = "text-embedding-004"
+    encoding_format: Optional[str] = "float"
+
+
+class ImageGenerationRequest(BaseModel):
+    model: str = "DALL-E-3"
+    prompt: str = ""
+    n: int = 1
+    size: Optional[str] = "1024x1024"
+    quality: Optional[str] = ""
+    style: Optional[str] = ""
+    response_format: Optional[str] = "url"