Merge branch 'main' into test

冲突解决：
- wire_gen.go: 合并 antigravityGatewayService 和 ProvideConcurrencyCache
- user_repo_integration_test.go: 保留 NotFound 测试
- antigravity_gateway_service.go: 适配 httpUpstream.Do 新签名

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

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

backend/internal/repository/account_repo.go

@@ -356,7 +356,7 @@ func (r *accountRepository) BatchUpdateLastUsed(ctx context.Context, updates map
 
 	idx := 1
 	for id, ts := range updates {
-		caseSQL += " WHEN $" + itoa(idx) + " THEN $" + itoa(idx+1)
+		caseSQL += " WHEN $" + itoa(idx) + " THEN $" + itoa(idx+1) + "::timestamptz"
 		args = append(args, id, ts)
 		ids = append(ids, id)
 		idx += 2