Refactor issue list (#32755)

1. add backend support for filtering "poster" and "assignee"
    * due to the limits, there is no frontend support at the moment
2. rewrite TS code without jquery, now there are 14 jQuery files left:

routers/web/shared/user/helper.go

@@ -4,7 +4,9 @@
 package user
 
 import (
+	"context"
 	"slices"
+	"strconv"
 
 	"code.gitea.io/gitea/models/user"
 )
@@ -24,3 +26,22 @@ func MakeSelfOnTop(doer *user.User, users []*user.User) []*user.User {
 	}
 	return users
 }
+
+// GetFilterUserIDByName tries to get the user ID from the given username.
+// Before, the "issue filter" passes user ID to query the list, but in many cases, it's impossible to pre-fetch the full user list.
+// So it's better to make it work like GitHub: users could input username directly.
+// Since it only converts the username to ID directly and is only used internally (to search issues), so no permission check is needed.
+// Old usage: poster=123, new usage: poster=the-username (at the moment, non-existing username is treated as poster=0, not ideal but acceptable)
+func GetFilterUserIDByName(ctx context.Context, name string) int64 {
+	if name == "" {
+		return 0
+	}
+	u, err := user.GetUserByName(ctx, name)
+	if err != nil {
+		if id, err := strconv.ParseInt(name, 10, 64); err == nil {
+			return id
+		}
+		return 0
+	}
+	return u.ID
+}