fix(canvas): 画布同步 - 素材缺失时可强制覆盖并恢复文本与连线顺序

云端缺少素材时可用本地版强制覆盖，只清失效媒体引用。文本节点不再把资源地址当正文，合并时保留引用槽位顺序。

web/test/user-data-sync-media.test.ts

@@ -0,0 +1,67 @@
+import { describe, expect, test } from "bun:test";
+
+import { ensureRemoteResourceReferences, restoreRemoteTextNodeContents } from "@/services/user-data-sync-media";
+
+describe("画布资源引用同步", () => {
+    test("文本节点保留正文，只同步资源定位键", async () => {
+        const node = {
+            type: "text",
+            metadata: {
+                content: "这是上传文件的正文",
+                prompt: "这是上传文件的正文",
+                storageKey: "resource:text-file",
+                mimeType: "text/plain",
+            },
+        };
+
+        const synced = await ensureRemoteResourceReferences(node);
+
+        expect(synced.metadata.content).toBe(node.metadata.content);
+        expect(synced.metadata.prompt).toBe(node.metadata.prompt);
+        expect(synced.metadata.storageKey).toBe("resource:text-file");
+    });
+
+    test("媒体节点仍将展示字段转换为资源地址", async () => {
+        const node = {
+            type: "image",
+            metadata: {
+                content: "blob:image",
+                storageKey: "resource:image-file",
+            },
+        };
+
+        const synced = await ensureRemoteResourceReferences(node);
+
+        expect(synced.metadata.content).toContain("/resources/image-file/file");
+    });
+
+    test("加载旧画布时恢复已被保存成资源 URL 的文本正文", async () => {
+        const project = {
+            nodes: [
+                {
+                    type: "text",
+                    metadata: {
+                        content: "/api/resources/text-file/file",
+                        prompt: "上传文件的原始正文",
+                        storageKey: "resource:text-file",
+                    },
+                },
+            ],
+        };
+
+        const restored = await restoreRemoteTextNodeContents(project, async () => null);
+
+        expect(restored.nodes[0].metadata.content).toBe("上传文件的原始正文");
+    });
+
+    test("没有可恢复的 prompt 时从资源文件读取正文", async () => {
+        const project = {
+            nodes: [{ type: "text", metadata: { content: "/api/resources/text-file/file", storageKey: "resource:text-file" } }],
+        };
+
+        const restored = await restoreRemoteTextNodeContents(project, async () => "从资源恢复的正文");
+
+        expect(restored.nodes[0].metadata.content).toBe("从资源恢复的正文");
+        expect(restored.nodes[0].metadata.prompt).toBe("从资源恢复的正文");
+    });
+});