chore(chart): set content type for charts

Author: Redume

chart/routes/get_chart.py

@@ -123,15 +123,18 @@ async def get_chart(req: Request, currency: Currency = Depends()) -> StreamingRe
         )
 
     chart = None
+    format = None # TODO: rewrite
     match currency.backend:
         case "typst":
             chart = await typst.create_chart(currency, dates, rates)
+            format = 'image/png'
         case "matplotlib":
             chart = await matplotlib.create_chart(currency, dates, rates)
+            format = 'image/jpeg'
 
     if chart is None:
         raise HTTPException(
             status_code=status.HTTP_400_BAD_REQUEST, detail="No data found."
         )
 
-    return StreamingResponse(chart)
+    return StreamingResponse(chart, media_type=format)