feat(favicon): add variant support for favicons

- Introduced a new Variant field in GetFavIconRequest to specify icon variants (light/dark).
- Updated GetFavIconFromAlias function to handle the variant when fetching favicons.
- Added WithVariant method in IconURL to manage icon variants effectively.

internal/homepage/icon_url.go

@@ -23,7 +23,8 @@ type (
 		IsDark   bool    `json:"is_dark"`
 	}
 
-	IconSource string
+	IconSource  string
+	IconVariant string
 )
 
 const (
@@ -33,6 +34,12 @@ const (
 	IconSourceSelfhSt   IconSource = "@selfhst"
 )
 
+const (
+	IconVariantNone  IconVariant = ""
+	IconVariantLight IconVariant = "light"
+	IconVariantDark  IconVariant = "dark"
+)
+
 var ErrInvalidIconURL = gperr.New("invalid icon url")
 
 func NewIconURL(source IconSource, refOrName, format string) *IconURL {
@@ -76,6 +83,28 @@ func (u *IconURL) HasIcon() bool {
 	return HasIcon(u)
 }
 
+func (u *IconURL) WithVariant(variant IconVariant) *IconURL {
+	var extra *IconExtra
+	if u.Extra != nil {
+		extra = &IconExtra{
+			Key:      u.Extra.Key,
+			Ref:      u.Extra.Ref,
+			FileType: u.Extra.FileType,
+		}
+		switch variant {
+		case IconVariantLight:
+			extra.IsLight = true
+		case IconVariantDark:
+			extra.IsDark = true
+		}
+	}
+	return &IconURL{
+		IconSource: u.IconSource,
+		FullURL:    u.FullURL,
+		Extra:      extra,
+	}
+}
+
 // Parse implements strutils.Parser.
 func (u *IconURL) Parse(v string) error {
 	return u.parse(v, true)