Add time.sleep after sd.cpp generation to let Vulkan driver settle

This helps prevent the GPU from staying at 100% utilization after
image generation by allowing the Vulkan driver to transition from
compute state to idle state.

coderai

@@ -3285,6 +3285,10 @@ async def create_image_generation(request: ImageGenerationRequest):
                     batch_count=request.n if request.n else 1,
                 )
                 
+                # Small delay to let Vulkan driver settle after generation
+                import time
+                time.sleep(0.1)
+                
                 # Convert results to response format
                 images = []
                 import base64
@@ -3373,6 +3377,10 @@ async def create_image_generation(request: ImageGenerationRequest):
                     batch_count=request.n if request.n else 1,
                 )
                 
+                # Small delay to let Vulkan driver settle after generation
+                import time
+                time.sleep(0.1)
+                
                 # Convert results to response format
                 images = []
                 import base64