Move web JSON functions to web context and simplify code (#26132)

The JSONRedirect/JSONOK/JSONError functions were put into "Base" context
incorrectly, it would cause abuse.

Actually, they are for "web context" only, so, move them to the correct
place.

And by the way, use them to simplify old code: +75 -196

modules/context/base.go

@@ -136,18 +136,6 @@ func (b *Base) JSON(status int, content any) {
 	}
 }
 
-func (b *Base) JSONRedirect(redirect string) {
-	b.JSON(http.StatusOK, map[string]any{"redirect": redirect})
-}
-
-func (b *Base) JSONOK() {
-	b.JSON(http.StatusOK, map[string]any{"ok": true}) // this is only a dummy response, frontend seldom uses it
-}
-
-func (b *Base) JSONError(msg string) {
-	b.JSON(http.StatusBadRequest, map[string]any{"errorMessage": msg})
-}
-
 // RemoteAddr returns the client machine ip address
 func (b *Base) RemoteAddr() string {
 	return b.Req.RemoteAddr