feat: 新增账单导出 Excel 功能

- 后端新增 /api/bills/export 接口，支持当前筛选条件导出全部记录
- 使用 excelize 库生成 xlsx 格式文件
- 前端账单管理页面添加导出按钮
- 更新 Go 版本到 1.24 以支持 excelize 依赖

server/go.mod

@@ -1,13 +1,13 @@
 module billai-server
 
-go 1.21
+go 1.24.0
 
 require (
 	github.com/gin-gonic/gin v1.9.1
 	github.com/golang-jwt/jwt/v5 v5.3.0
 	github.com/yeka/zip v0.0.0-20231116150916-03d6312748a9
 	go.mongodb.org/mongo-driver v1.13.1
-	golang.org/x/text v0.9.0
+	golang.org/x/text v0.34.0
 	gopkg.in/yaml.v3 v3.0.1
 )
 
@@ -30,16 +30,22 @@ require (
 	github.com/modern-go/reflect2 v1.0.2 // indirect
 	github.com/montanaflynn/stats v0.0.0-20171201202039-1bf9dbcd8cbe // indirect
 	github.com/pelletier/go-toml/v2 v2.0.8 // indirect
+	github.com/richardlehane/mscfb v1.0.6 // indirect
+	github.com/richardlehane/msoleps v1.0.6 // indirect
+	github.com/tiendc/go-deepcopy v1.7.2 // indirect
 	github.com/twitchyliquid64/golang-asm v0.15.1 // indirect
 	github.com/ugorji/go/codec v1.2.11 // indirect
 	github.com/xdg-go/pbkdf2 v1.0.0 // indirect
 	github.com/xdg-go/scram v1.1.2 // indirect
 	github.com/xdg-go/stringprep v1.0.4 // indirect
+	github.com/xuri/efp v0.0.1 // indirect
+	github.com/xuri/excelize/v2 v2.10.1 // indirect
+	github.com/xuri/nfp v0.0.2-0.20250530014748-2ddeb826f9a9 // indirect
 	github.com/youmark/pkcs8 v0.0.0-20181117223130-1be2e3e5546d // indirect
 	golang.org/x/arch v0.3.0 // indirect
-	golang.org/x/crypto v0.9.0 // indirect
-	golang.org/x/net v0.10.0 // indirect
-	golang.org/x/sync v0.0.0-20220722155255-886fb9371eb4 // indirect
-	golang.org/x/sys v0.8.0 // indirect
+	golang.org/x/crypto v0.48.0 // indirect
+	golang.org/x/net v0.50.0 // indirect
+	golang.org/x/sync v0.19.0 // indirect
+	golang.org/x/sys v0.41.0 // indirect
 	google.golang.org/protobuf v1.30.0 // indirect
 )