feat(prompt): AI 提示词优化双栏交互

新增 prompt API 模块调用后端 /api/v1/prompt/optimize，PromptEditor
重构为左右双栏布局支持原始/优化提示词对比编辑，默认开启 AI 优化，
用户可关闭开关或手动编辑优化结果后再提交生成。

frontend/src/components/GenerateForm.tsx

@@ -13,7 +13,7 @@ const ASSET_TYPES: { value: AssetType; label: string }[] = [
 ]
 
 interface GenerateFormProps {
-  onSubmit: () => void
+  onSubmit: (prompt: string) => void
   submitting: boolean
 }
 
@@ -24,13 +24,32 @@ export default function GenerateForm({ onSubmit, submitting }: GenerateFormProps
     assetType,
     taskStyle,
     params,
+    enableAI,
+    optimizedPrompt,
+    isOptimizing,
     setPrompt,
     setAssetType,
     toggleTaskStyle,
     setParams,
+    setEnableAI,
+    setOptimizedPrompt,
+    runOptimize,
   } = useTaskStore()
 
   const mergedStyle = mergeStyles(projectStyle, taskStyle)
+  const finalPrompt = enableAI && optimizedPrompt ? optimizedPrompt : prompt
+
+  const handleOptimize = async () => {
+    try {
+      await runOptimize(projectStyle)
+    } catch {
+      // error handled in store
+    }
+  }
+
+  const handleSubmit = () => {
+    onSubmit(finalPrompt)
+  }
 
   return (
     <div style={{ display: 'flex', flexDirection: 'column', gap: 24 }}>
@@ -62,16 +81,41 @@ export default function GenerateForm({ onSubmit, submitting }: GenerateFormProps
         <StyleSelector value={taskStyle} onChange={toggleTaskStyle} compact />
       </div>
 
-      {/* 提示词 */}
+      {/* 提示词（含 AI 优化） */}
       <div>
-        <h3 style={{ marginBottom: 12, fontSize: 14, color: 'var(--text-secondary)' }}>
-          提示词
-        </h3>
+        <div
+          style={{
+            display: 'flex',
+            justifyContent: 'space-between',
+            alignItems: 'center',
+            marginBottom: 12,
+          }}
+        >
+          <h3 style={{ fontSize: 14, color: 'var(--text-secondary)' }}>
+            提示词
+          </h3>
+          {enableAI && (
+            <button
+              type="button"
+              className="btn-secondary"
+              onClick={handleOptimize}
+              disabled={isOptimizing || !prompt.trim()}
+              style={{ padding: '6px 16px', fontSize: 13 }}
+            >
+              {isOptimizing ? '优化中...' : '优化提示词'}
+            </button>
+          )}
+        </div>
         <PromptEditor
           prompt={prompt}
           onPromptChange={setPrompt}
           style={mergedStyle}
           params={{ resolution: params.resolution, format: params.format }}
+          enableAI={enableAI}
+          onEnableAIToggle={setEnableAI}
+          optimizedPrompt={optimizedPrompt}
+          isOptimizing={isOptimizing}
+          onOptimizedPromptChange={setOptimizedPrompt}
         />
       </div>
 
@@ -113,8 +157,8 @@ export default function GenerateForm({ onSubmit, submitting }: GenerateFormProps
       <button
         type="button"
         className="btn-primary"
-        onClick={onSubmit}
-        disabled={submitting || !prompt.trim()}
+        onClick={handleSubmit}
+        disabled={submitting || !finalPrompt.trim()}
         style={{ alignSelf: 'flex-start', padding: '12px 32px', fontSize: 16 }}
       >
         {submitting ? '提交中...' : '开始生成'}