fix: 安全审查 P3 问题修复（10项）

无障碍与用户体验：
- 补全 OnboardingView/ProcessingView/ResultView/WallpaperGuideView 无障碍标注
- ContentView 添加后台切换截屏保护（模糊覆盖层）
- EditorView iPad 右侧面板改为响应式宽度（minWidth:320, maxWidth:420）
- ResultView CelebrationParticles 改用 Task 替代 DispatchQueue 延迟
- DesignSystem accessibility key 从中文改为英文
- EditorView/WallpaperGuideView 生成按钮 accentColor 统一为设计系统
- OnboardingView 第四页添加相册权限预告提示

核心库优化：
- LivePhotoLogger 添加日志安全注释
- CacheManager.makeWorkPaths 添加磁盘空间预检查（<500MB 报错）
- ImageFormatConverter BGRA/ARGB 转换改用 vImagePermuteChannels 加速

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Sources/LivePhotoCore/AIEnhancer/ImageFormatConverter.swift

@@ -212,21 +212,25 @@ enum ImageFormatConverter {
         bytesPerRow: Int
     ) -> [UInt8] {
         var result = [UInt8](repeating: 0, count: width * height * 4)
+        let dstBytesPerRow = width * 4
 
-        for y in 0..<height {
-            let srcRow = baseAddress.advanced(by: y * bytesPerRow).assumingMemoryBound(to: UInt8.self)
-            let dstOffset = y * width * 4
+        var srcBuffer = vImage_Buffer(
+            data: baseAddress,
+            height: vImagePixelCount(height),
+            width: vImagePixelCount(width),
+            rowBytes: bytesPerRow
+        )
 
-            for x in 0..<width {
-                let srcIdx = x * 4
-                let dstIdx = dstOffset + x * 4
-
-                // BGRA -> RGBA swap
-                result[dstIdx + 0] = srcRow[srcIdx + 2]  // R
-                result[dstIdx + 1] = srcRow[srcIdx + 1]  // G
-                result[dstIdx + 2] = srcRow[srcIdx + 0]  // B
-                result[dstIdx + 3] = srcRow[srcIdx + 3]  // A
-            }
+        result.withUnsafeMutableBufferPointer { dstPtr in
+            var dstBuffer = vImage_Buffer(
+                data: dstPtr.baseAddress!,
+                height: vImagePixelCount(height),
+                width: vImagePixelCount(width),
+                rowBytes: dstBytesPerRow
+            )
+            // BGRA → RGBA: 通道重排 [2,1,0,3]
+            let permuteMap: [UInt8] = [2, 1, 0, 3]
+            vImagePermuteChannels_ARGB8888(&srcBuffer, &dstBuffer, permuteMap, vImage_Flags(kvImageNoFlags))
         }
 
         return result
@@ -239,21 +243,25 @@ enum ImageFormatConverter {
         bytesPerRow: Int
     ) -> [UInt8] {
         var result = [UInt8](repeating: 0, count: width * height * 4)
+        let dstBytesPerRow = width * 4
 
-        for y in 0..<height {
-            let srcRow = baseAddress.advanced(by: y * bytesPerRow).assumingMemoryBound(to: UInt8.self)
-            let dstOffset = y * width * 4
+        var srcBuffer = vImage_Buffer(
+            data: baseAddress,
+            height: vImagePixelCount(height),
+            width: vImagePixelCount(width),
+            rowBytes: bytesPerRow
+        )
 
-            for x in 0..<width {
-                let srcIdx = x * 4
-                let dstIdx = dstOffset + x * 4
-
-                // ARGB -> RGBA swap
-                result[dstIdx + 0] = srcRow[srcIdx + 1]  // R
-                result[dstIdx + 1] = srcRow[srcIdx + 2]  // G
-                result[dstIdx + 2] = srcRow[srcIdx + 3]  // B
-                result[dstIdx + 3] = srcRow[srcIdx + 0]  // A
-            }
+        result.withUnsafeMutableBufferPointer { dstPtr in
+            var dstBuffer = vImage_Buffer(
+                data: dstPtr.baseAddress!,
+                height: vImagePixelCount(height),
+                width: vImagePixelCount(width),
+                rowBytes: dstBytesPerRow
+            )
+            // ARGB → RGBA: 通道重排 [1,2,3,0]
+            let permuteMap: [UInt8] = [1, 2, 3, 0]
+            vImagePermuteChannels_ARGB8888(&srcBuffer, &dstBuffer, permuteMap, vImage_Flags(kvImageNoFlags))
         }
 
         return result

Sources/LivePhotoCore/LivePhotoCore.swift

@@ -260,6 +260,18 @@ public struct CacheManager: Sendable {
     }
 
     public func makeWorkPaths(workId: UUID) throws -> LivePhotoWorkPaths {
+        // 检查可用磁盘空间（视频处理需要约 500MB 临时空间）
+        let resourceValues = try baseDirectory.resourceValues(forKeys: [.volumeAvailableCapacityForImportantUsageKey])
+        if let availableCapacity = resourceValues.volumeAvailableCapacityForImportantUsage,
+           availableCapacity < 500_000_000 {
+            throw AppError(
+                code: "LPB-001",
+                stage: .normalize,
+                message: String(localized: "error.insufficientDiskSpace"),
+                suggestedActions: [String(localized: "error.clearCache"), String(localized: "error.freeSpace")]
+            )
+        }
+
         let workDir = baseDirectory.appendingPathComponent(workId.uuidString, isDirectory: true)
         try FileManager.default.createDirectory(at: workDir, withIntermediateDirectories: true)
         return LivePhotoWorkPaths(
@@ -291,10 +303,14 @@ public struct LivePhotoLogger: Sendable {
         self.logger = os.Logger(subsystem: subsystem, category: category)
     }
 
+    /// 记录信息级别日志
+    /// - Important: 日志使用 .public 隐私级别，不要在消息中包含用户输入内容、个人信息或文件路径中的用户名
     public func info(_ message: String) {
         logger.info("\(message, privacy: .public)")
     }
 
+    /// 记录错误级别日志
+    /// - Important: 日志使用 .public 隐私级别，不要在消息中包含用户输入内容、个人信息或文件路径中的用户名
     public func error(_ message: String) {
         logger.error("\(message, privacy: .public)")
     }