feat: Add inpainting (局部重绘) feature for timeline editor

- Add canvas-based mask drawing tools (brush, eraser, rect, lasso)
- Add undo/redo history support for mask editing
- Integrate inpainting UI into preview player
- Add backend API endpoint for inpainting requests
- Add MediaService.inpaint method with ComfyUI workflow support
- Add Flux inpainting workflows for selfhost and RunningHub

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

pixelle_video/services/media.py

@@ -285,3 +285,76 @@ class MediaService(ComfyBaseService):
         except Exception as e:
             logger.error(f"Media generation error: {e}")
             raise
+
+    async def inpaint(
+        self,
+        image_path: str,
+        mask_path: str,
+        prompt: Optional[str] = None,
+        denoise_strength: float = 0.8,
+        workflow: Optional[str] = None,
+        **params
+    ) -> MediaResult:
+        """
+        Inpaint image using mask
+
+        Args:
+            image_path: Path to original image
+            mask_path: Path to mask image (white=inpaint, black=keep)
+            prompt: Optional prompt for inpainted region
+            denoise_strength: How much to change masked area (0.0-1.0)
+            workflow: Inpainting workflow to use
+
+        Returns:
+            MediaResult with inpainted image URL
+        """
+        logger.info(f"🎨 Inpainting image: {image_path}")
+        logger.info(f"   Mask: {mask_path}")
+        logger.info(f"   Denoise: {denoise_strength}")
+
+        try:
+            # Resolve workflow
+            if workflow is None:
+                workflow = "selfhost/image_inpaint_flux.json"
+
+            workflow_info = self._resolve_workflow(workflow=workflow)
+
+            # Build workflow parameters
+            workflow_params = {
+                "image": image_path,
+                "mask": mask_path,
+                "denoise": denoise_strength,
+            }
+
+            if prompt:
+                workflow_params["prompt"] = prompt
+
+            workflow_params.update(params)
+
+            logger.debug(f"Inpaint workflow parameters: {workflow_params}")
+
+            # Execute workflow
+            kit = await self.core._get_or_create_comfykit()
+
+            if workflow_info["source"] == "runninghub" and "workflow_id" in workflow_info:
+                workflow_input = workflow_info["workflow_id"]
+            else:
+                workflow_input = workflow_info["path"]
+
+            result = await kit.execute(workflow_input, workflow_params)
+
+            if not result.images:
+                logger.error("No image generated from inpainting")
+                raise Exception("Inpainting failed - no image generated")
+
+            image_url = result.images[0]
+            logger.info(f"✅ Inpainted image: {image_url}")
+
+            return MediaResult(
+                media_type="image",
+                url=image_url
+            )
+
+        except Exception as e:
+            logger.error(f"Inpainting error: {e}")
+            raise