fix(agetn features):

1. Historical multimodal message writing is incorporated into the conversation context;
2. Resolve the issues where csv, json, and txt files cannot be recognized due to encoding problems;
3. File quantity limit;
4. Error details

api/app/schemas/app_schema.py

@@ -151,7 +151,7 @@ class FileUploadConfig(BaseModel):
     document_enabled: bool = Field(default=False)
     document_max_size_mb: int = Field(default=100)
     document_allowed_extensions: List[str] = Field(
-        default=["pdf", "docx", "xlsx", "txt", "csv", "json", "md"]
+        default=["pdf", "docx", "doc", "xlsx", "xls", "txt", "csv", "json", "md"]
     )
     # 视频文件：MP4/MOV/AVI/WebM，最大 500MB
     video_enabled: bool = Field(default=False)
@@ -160,7 +160,15 @@ class FileUploadConfig(BaseModel):
         default=["mp4", "mov"]
     )
     # 最大文件数量
-    max_file_count: int = Field(default=5, ge=1, le=20)
+    max_file_count: int = Field(default=5, ge=1)
+
+    @field_validator("max_file_count")
+    @classmethod
+    def validate_max_file_count(cls, v: int) -> int:
+        from app.core.config import settings
+        if v > settings.MAX_FILE_COUNT:
+            raise ValueError(f"max_file_count 不能超过 {settings.MAX_FILE_COUNT}")
+        return v
 
 
 class OpeningStatementConfig(BaseModel):