Fix notifications pagination query parameters (#36351)

Fix #36350

services/context/pagination_test.go

@@ -0,0 +1,35 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package context
+
+import (
+	"net/url"
+	"testing"
+
+	"code.gitea.io/gitea/modules/container"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestPagination(t *testing.T) {
+	p := NewPagination(1, 1, 1, 1)
+	params := url.Values{}
+	params.Add("k1", "11")
+	params.Add("k1", "12")
+	params.Add("k", "a")
+	params.Add("k", "b")
+	params.Add("k2", "21")
+	params.Add("k2", "22")
+	params.Add("foo", "bar")
+
+	p.AddParamFromQuery(params)
+	v, _ := url.ParseQuery(string(p.GetParams()))
+	assert.Equal(t, params, v)
+
+	p.RemoveParam(container.SetOf("k", "foo"))
+	params.Del("k")
+	params.Del("foo")
+	v, _ = url.ParseQuery(string(p.GetParams()))
+	assert.Equal(t, params, v)
+}