Move internal packages to an internal folder

For reference: https://go.dev/doc/go1.4#internalpackages

ui/pagination.go

@@ -1,42 +0,0 @@
-// SPDX-FileCopyrightText: Copyright The Miniflux Authors. All rights reserved.
-// SPDX-License-Identifier: Apache-2.0
-
-package ui // import "miniflux.app/v2/ui"
-
-type pagination struct {
-	Route        string
-	Total        int
-	Offset       int
-	ItemsPerPage int
-	ShowNext     bool
-	ShowPrev     bool
-	NextOffset   int
-	PrevOffset   int
-	SearchQuery  string
-}
-
-func getPagination(route string, total, offset, nbItemsPerPage int) pagination {
-	nextOffset := 0
-	prevOffset := 0
-	showNext := (total - offset) > nbItemsPerPage
-	showPrev := offset > 0
-
-	if showNext {
-		nextOffset = offset + nbItemsPerPage
-	}
-
-	if showPrev {
-		prevOffset = offset - nbItemsPerPage
-	}
-
-	return pagination{
-		Route:        route,
-		Total:        total,
-		Offset:       offset,
-		ItemsPerPage: nbItemsPerPage,
-		ShowNext:     showNext,
-		NextOffset:   nextOffset,
-		ShowPrev:     showPrev,
-		PrevOffset:   prevOffset,
-	}
-}