change posterror back to apperror

src/main.rs

@@ -63,7 +63,7 @@ struct ViewPostTemplate {
     markdown_access: bool,
 }
 
-type AppResult<T> = Result<T, PostError>;
+type AppResult<T> = Result<T, AppError>;
 
 #[derive(Error, Debug)]
 enum AppError {
@@ -71,6 +71,13 @@ enum AppError {
     PostError(#[from] PostError),
 }
 
+impl From<std::io::Error> for AppError {
+    #[inline(always)]
+    fn from(value: std::io::Error) -> Self {
+        Self::PostError(PostError::IoError(value))
+    }
+}
+
 #[derive(Template)]
 #[template(path = "error.html")]
 struct ErrorTemplate {