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>

frontend/src/services/editor-api.ts

@@ -31,6 +31,11 @@ export interface PreviewResponse {
     frames_count: number
 }
 
+export interface InpaintResponse {
+    image_path: string
+    success: boolean
+}
+
 class EditorApiClient {
     private baseUrl: string
 
@@ -191,6 +196,37 @@ class EditorApiClient {
 
         return response.json()
     }
+
+    /**
+     * Inpaint (局部重绘) image for a frame
+     */
+    async inpaintImage(
+        storyboardId: string,
+        frameId: string,
+        mask: string,
+        prompt?: string,
+        denoiseStrength?: number
+    ): Promise<InpaintResponse> {
+        const response = await fetch(
+            `${this.baseUrl}/editor/storyboard/${storyboardId}/frames/${frameId}/inpaint`,
+            {
+                method: 'POST',
+                headers: { 'Content-Type': 'application/json' },
+                body: JSON.stringify({
+                    mask,
+                    prompt,
+                    denoise_strength: denoiseStrength ?? 0.8,
+                }),
+            }
+        )
+
+        if (!response.ok) {
+            const error = await response.json().catch(() => ({ detail: response.statusText }))
+            throw new Error(error.detail || `Failed to inpaint image: ${response.statusText}`)
+        }
+
+        return response.json()
+    }
 }
 
 // Export singleton instance