fix: 转存时先查资源历史, 复用原账号; save_records加config_id

- 资源维度优先级 > IP维度: 先查share_url是否被转存过
- save_records 表新增 config_id 字段 + 写入时记录
- cloud.service.ts 所有 INSERT 写入 config.id
- credential.service.ts: getAndValidateCredential 加 shareUrl 参数
- 数据库 migration: config_id 到 save_records

packages/backend/src/cloud/credential.service.ts

@@ -423,11 +423,38 @@ export interface CredentialValidationResult {
  * 
  * Reference: search-ucmao get_and_validate_credential() pattern.
  */
-export async function getAndValidateCredential(cloudType: string, ipAddress?: string): Promise<CredentialValidationResult> {
+export async function getAndValidateCredential(cloudType: string, ipAddress?: string, shareUrl?: string): Promise<CredentialValidationResult> {
   const db = getDb();
 
   let config: CloudConfig | undefined;
 
+  // ── Resource history lookup: if this share URL was saved before, reuse that account ──
+  if (shareUrl) {
+    const historyRecord = db.prepare(
+      `SELECT config_id, target_cloud, folder_name FROM save_records
+       WHERE share_url = ? AND target_cloud = ? AND status IN ('success', 'reused')
+       ORDER BY id DESC LIMIT 1`
+    ).get(shareUrl, cloudType) as { config_id: number; target_cloud: string; folder_name: string } | undefined;
+
+    if (historyRecord) {
+      // Resource was previously saved — reuse the exact same config if still healthy
+      if (historyRecord.config_id) {
+        config = db.prepare(
+          `SELECT * FROM cloud_configs WHERE id = ? AND is_active = 1 AND consecutive_failures < 5`
+        ).get(historyRecord.config_id) as CloudConfig | undefined;
+      }
+      if (!config) {
+        // Fallback: pick any healthy account from this cloud type
+        config = db.prepare(
+          `SELECT * FROM cloud_configs
+           WHERE cloud_type = ? AND is_active = 1 AND consecutive_failures < 5
+           ORDER BY is_primary DESC, last_used_at ASC NULLS FIRST
+           LIMIT 1`
+        ).get(cloudType) as CloudConfig | undefined;
+      }
+    }
+  }
+
   if (!ipAddress) {
     // No IP info — fallback to simple LUR
     config = db.prepare(