Implement friend APIs and target profile support

- Add friend search/list/request/requestCancel/response/expel handlers and schemas
- Store friend relationships in user_friend and backfill default friend links at startup
- Auto-add the default user as a friend for newly created accounts
- Support target user_id in /api profile requests and return target profile data
- Make profile accessory_info optional to avoid zero-value accessory payloads
- Update login topInfo friend counters from friend relationship state

Signed-off-by: Sean Du <do4suki@gmail.com>

internal/handler/api/profile/profile.go

@@ -6,14 +6,14 @@ import (
 	"github.com/gin-gonic/gin"
 )
 
-func ProfileApi(ctx *gin.Context, action string) (res any, err error) {
+func ProfileApi(ctx *gin.Context, action string, targetUserID int) (res any, err error) {
 	switch action {
 	case "cardRanking":
 		res, err = cardRanking()
 	case "liveCnt":
 		res, err = liveCnt()
 	case "profileInfo":
-		res, err = profileInfo(ctx)
+		res, err = profileInfo(ctx, targetUserID)
 	default:
 		err = fmt.Errorf("unimplemented action: profile: %s", action)
 	}