better timeout handling

src/main.py

@@ -159,7 +159,7 @@ async def generate(
     }
 
     start_time = time.monotonic()
-
+    try:
         async with aiohttp.ClientSession() as session:
             async with session.post(
                 "https://image.novelai.net/ai/generate-image",
@@ -169,6 +169,10 @@ async def generate(
             ) as response:
                 response_bytes = await response.read()
                 status_code = response.status
+    except aiohttp.TimeoutError:
+        await interaction.followup.send("Error: the request timed out.")
+    except aiohttp.ClientError as e:
+        await interaction.followup.send(f"Error: {e}")
 
     duration = time.monotonic() - start_time
     logger.info("Image creation took %.2f seconds", duration)