Use DPM++ scheduler when IP-Adapter disabled

DPMSolverMultistepScheduler produces sharper, higher quality output.
This matches the original dreamtail configuration that produced
excellent results.

worker/generator.py

@@ -11,7 +11,7 @@ import cv2
 import numpy as np
 from typing import Optional, Dict, Any, List, Union
 from pathlib import Path
-from diffusers import StableDiffusionXLPipeline, DDIMScheduler
+from diffusers import StableDiffusionXLPipeline, DDIMScheduler, DPMSolverMultistepScheduler
 from PIL import Image
 import asyncio
 
@@ -83,7 +83,7 @@ class SDXLGenerator:
                         add_watermarker=False,
                     )
                 else:
-                    # Use model's default scheduler for best quality
+                    # Use model's default scheduler, then switch to DPM++ for best quality
                     self.pipeline = StableDiffusionXLPipeline.from_pretrained(
                         config.SDXL_MODEL_ID,
                         torch_dtype=dtype,
@@ -91,6 +91,11 @@ class SDXLGenerator:
                         cache_dir=str(config.MODELS_DIR),
                         add_watermarker=False,
                     )
+                    # Use DPM++ scheduler for better quality/speed
+                    self.pipeline.scheduler = DPMSolverMultistepScheduler.from_config(
+                        self.pipeline.scheduler.config
+                    )
+                    logger.info("Using DPM++ scheduler for best quality")
 
                 # Move to device
                 self.pipeline = self.pipeline.to(self.device)