misc: Decouple Grid view from Albums

The Grid view and related components were highly coupled to Albums,
including the filter button that is currently used only for album
filtering.

As part of the migration of Artists to Grid view, this is the smallest
possible change to convert many of the existing code to
generics/interfaces that will allow different media to be displayed and
filtered by using Grid views.

The main changes in this diff are:

* Introduction of generics for Media types (`M`) and Filter options
  (`F`), which can be later extended to other entities besides Albums.
* Complete decoupling of `GridViewPage` and related components from
  Albums (making these pages also generic).
* Refactoring of Subsonic/Jellyfin specific code to understand these new
  generics when dealing with filtering logic.

backend/mediaprovider/mediaprovider.go

@@ -7,7 +7,24 @@ import (
 	"strings"
 )
 
-type AlbumFilter struct {
+type MediaIterator[M any] interface {
+	Next() *M
+}
+
+type ArtistIterator = MediaIterator[Artist]
+type AlbumIterator = MediaIterator[Album]
+type TrackIterator = MediaIterator[Track]
+
+type MediaFilter[M, F any] interface {
+	Options() F
+	SetOptions(F)
+	IsNil() bool
+	Matches(*M) bool
+}
+
+type AlbumFilter = MediaFilter[Album, AlbumFilterOptions]
+
+type AlbumFilterOptions struct {
 	MinYear int
 	MaxYear int      // 0 == unset/match any
 	Genres  []string // len(0) == unset/match any
@@ -16,42 +33,46 @@ type AlbumFilter struct {
 	ExcludeUnfavorited bool // mut. exc. with ExcludeFavorited
 }
 
-// Returns true if the filter is the nil filter - i.e. matches everything
-func (a AlbumFilter) IsNil() bool {
-	return a.MinYear == 0 && a.MaxYear == 0 &&
-		len(a.Genres) == 0 &&
-		!a.ExcludeFavorited && !a.ExcludeUnfavorited
+type albumFilter struct {
+	options AlbumFilterOptions
 }
 
-func (f AlbumFilter) Matches(album *Album) bool {
+func NewAlbumFilter(options AlbumFilterOptions) *albumFilter {
+	return &albumFilter{options}
+}
+
+func (a albumFilter) Options() AlbumFilterOptions {
+	return a.options
+}
+
+func (a *albumFilter) SetOptions(o AlbumFilterOptions) {
+	a.options = o
+}
+
+// Returns true if the filter is the nil filter - i.e. matches everything
+func (a albumFilter) IsNil() bool {
+	return a.options.MinYear == 0 && a.options.MaxYear == 0 &&
+		len(a.options.Genres) == 0 &&
+		!a.options.ExcludeFavorited && !a.options.ExcludeUnfavorited
+}
+
+func (f albumFilter) Matches(album *Album) bool {
 	if album == nil {
 		return false
 	}
-	if f.ExcludeFavorited && album.Favorite {
+	if f.options.ExcludeFavorited && album.Favorite {
 		return false
 	}
-	if f.ExcludeUnfavorited && !album.Favorite {
+	if f.options.ExcludeUnfavorited && !album.Favorite {
 		return false
 	}
-	if y := album.Year; y < f.MinYear || (f.MaxYear > 0 && y > f.MaxYear) {
+	if y := album.Year; y < f.options.MinYear || (f.options.MaxYear > 0 && y > f.options.MaxYear) {
 		return false
 	}
-	if len(f.Genres) == 0 {
+	if len(f.options.Genres) == 0 {
 		return true
 	}
-	return genresMatch(f.Genres, album.Genres)
-}
-
-type ArtistIterator interface {
-	Next() *Artist
-}
-
-type AlbumIterator interface {
-	Next() *Album
-}
-
-type TrackIterator interface {
-	Next() *Track
+	return genresMatch(f.options.Genres, album.Genres)
 }
 
 type RatingFavoriteParameters struct {