fix: reset project completed status when order expires or refunds

[q3cc]

Problem

When users reserve paid CDK items but don't complete payment, the following issue occurs:

1. User reserves an item → item is LPOPed from Redis
2. All items are reserved → Redis stock becomes 0
3. One user completes payment → project is marked as IsCompleted=true
4. Other orders expire after 15 minutes → items are RPushed back to Redis
5. Issue: IsCompleted remains true even though Redis has stock again
6. Result: Frontend shows "Project Completed" and users cannot claim available items

例行检查

• x 我已阅读并理解 贡献者公约，
• x 我已阅读并同意 贡献者许可协议 (CLA)，确认我的贡献将根据项目的 MIT 许可证进行许可，
• x 我知晓如果此 PR 并不做出实质性更改，或可被认为是为了PR被合并而提交PR的，则可能不会被合并，

Root Cause

• FulfillForReceiver() sets IsCompleted=true when Redis stock is 0
• expireOrder() returns items to Redis but doesn't reset IsCompleted
• Frontend checks is_completed field and disables the claim button
• Backend only checks Redis stock in IsReceivable(), not IsCompleted

Solution

Added logic to check and reset IsCompleted when items are returned to inventory:

Changes

1. tasks.go: Added resetProjectCompletedStatus()

   • Called after expireOrder() returns items to Redis
   • Checks if project has IsCompleted=true but Redis has stock
   • Resets IsCompleted=false if condition met

2. service.go: Added resetProjectCompletedStatusAfterRefund()

   • Called when refund succeeds and items are returned
   • Handles both immediate refund and retry scenarios
   • Same logic as expiration cleanup

Testing

• ✅ Compiled successfully without errors
• ✅ Logic verified for both expiration and refund paths
• ✅ CAS update with WHERE clause ensures idempotency

Impact

• Projects will correctly show as available after expired orders release items
• No breaking changes to existing functionality
• Minimal performance impact (one query per expired order)

Fixes the issue where legitimate users cannot claim items that become available after order expiration.

[q3cc]

看起来 在 LDC 系统中 支付过期时间是 5 分钟 为什么这里 15 分钟才回放（）

[yyg-max]

1.resetProjectCompletedStatusAfterRefund和resetProjectCompletedStatus合并为一个放到Project当作函数方法/放utils.go
2.补上合适的事务

[yyg-max]

事务还是没看到，可以参考项目写的