Add option to filter board cards by labels and assignees (#31999)

Works in both organization and repository project boards

Fixes #21846

Replaces #21963
Replaces #27117
 

![image](https://github.com/user-attachments/assets/1837ace8-3de2-444f-a153-e166bd0da2c0)

**Note** that implementation was made intentionally to work same as in
issue list so that URL can be bookmarked for quick access with
predefined filters in URL

routers/web/repo/helper.go

@@ -5,25 +5,11 @@ package repo
 
 import (
 	"net/url"
-	"sort"
 
-	"code.gitea.io/gitea/models/user"
 	"code.gitea.io/gitea/modules/git"
 	"code.gitea.io/gitea/services/context"
 )
 
-func MakeSelfOnTop(doer *user.User, users []*user.User) []*user.User {
-	if doer != nil {
-		sort.Slice(users, func(i, j int) bool {
-			if users[i].ID == users[j].ID {
-				return false
-			}
-			return users[i].ID == doer.ID // if users[i] is self, put it before others, so less=true
-		})
-	}
-	return users
-}
-
 func HandleGitError(ctx *context.Context, msg string, err error) {
 	if git.IsErrNotExist(err) {
 		refType := ""