feat: update metadata field names to use mime_type and mime_encoding

src/modes/server/api/item.rs

@@ -505,7 +505,7 @@ async fn get_item_raw_content(item: &db::Item, data_dir: &PathBuf, conn: &mut ru
     
     let mime_type = meta_entries
         .iter()
-        .find(|m| m.name == "file.mime")
+        .find(|m| m.name == "mime_type")
         .map(|m| m.value.clone())
         .unwrap_or_else(|| "application/octet-stream".to_string());