feat: 实现真正的分块处理优化 AI 增强质量

- TiledImageProcessor 重写：将大图拆分为 512×512 重叠 tiles
- 64px 重叠区域 + 线性权重混合，消除拼接接缝
- AIEnhancer 自动选择处理器：大图用 TiledImageProcessor，小图用 WholeImageProcessor
- 信息损失从 ~86% 降至 0%（1080×1920 图像不再压缩到 288×512）

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

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

Sources/LivePhotoCore/AIEnhancer/RealESRGANProcessor.swift

@@ -29,7 +29,7 @@ actor RealESRGANProcessor {
 
     init() {}
 
-    /// Load Core ML model from bundle
+    /// Load Core ML model from ODR or bundle
     func loadModel() async throws {
         guard model == nil else {
             logger.debug("Model already loaded")
@@ -38,30 +38,34 @@ actor RealESRGANProcessor {
 
         logger.info("Loading Real-ESRGAN Core ML model...")
 
-        // Try to find model in bundle
-        let modelName = "RealESRGAN_x4plus"
-        var modelURL: URL?
-
-        // Try SPM bundle first
-        #if SWIFT_PACKAGE
-            if let url = Bundle.module.url(forResource: modelName, withExtension: "mlmodelc") {
-                modelURL = url
-            } else if let url = Bundle.module.url(forResource: modelName, withExtension: "mlpackage") {
-                modelURL = url
-            }
-        #endif
-
-        // Try main bundle
+        // 1. Try ODRManager first (supports both ODR download and bundle fallback)
+        var modelURL = await ODRManager.shared.getModelURL()
+        
+        // 2. If ODRManager returns nil, try direct bundle lookup as fallback
         if modelURL == nil {
+            let modelName = "RealESRGAN_x4plus"
+            
+            // Try main bundle
             if let url = Bundle.main.url(forResource: modelName, withExtension: "mlmodelc") {
                 modelURL = url
             } else if let url = Bundle.main.url(forResource: modelName, withExtension: "mlpackage") {
                 modelURL = url
             }
+            
+            // Try SPM bundle (development)
+            #if SWIFT_PACKAGE
+            if modelURL == nil {
+                if let url = Bundle.module.url(forResource: modelName, withExtension: "mlmodelc") {
+                    modelURL = url
+                } else if let url = Bundle.module.url(forResource: modelName, withExtension: "mlpackage") {
+                    modelURL = url
+                }
+            }
+            #endif
         }
 
         guard let url = modelURL else {
-            logger.error("Model file not found: \(modelName)")
+            logger.error("Model not found. Please download the AI model first.")
             throw AIEnhanceError.modelNotFound
         }