feat(ui): limit visible reactions and overhaul retro theme

- Limit the number of initially visible reactions per file to 2 and calculate the overflow count on the backend.
- Redesign the retro theme CSS to mimic a classic Windows 98 Explorer window, including title bars, toolbars, and sunken panes.
- Add local storage persistence for the file browser view preference (list vs. thumbnails).

backend/libs/handlers/download.go

@@ -50,6 +50,7 @@ type fileView struct {
 	IconRetroURL string
 	ReactURL     string
 	Reactions    []reactionView
+	ReactionMore int
 	Reacted      bool
 }
 
@@ -58,6 +59,7 @@ type reactionView struct {
 	URL     string `json:"url"`
 	Label   string `json:"label"`
 	Count   int    `json:"count"`
+	Visible bool   `json:"visible"`
 }
 
 type emojiTabView struct {
@@ -354,6 +356,7 @@ func (a *App) fileView(box services.Box, file services.File) fileView {
 
 func (a *App) fileViewWithReactions(box services.Box, file services.File, reactions []services.ReactionSummary, reacted bool) fileView {
 	icon := a.fileIcons.lookup(file.Name, file.ContentType)
+	reactionViews := a.reactionViews(reactions)
 	return fileView{
 		ID:           file.ID,
 		Name:         file.Name,
@@ -367,7 +370,8 @@ func (a *App) fileViewWithReactions(box services.Box, file services.File, reacti
 		IconURL:      fileIconURL("standard", icon.Standard),
 		IconRetroURL: fileIconURL("retro", icon.Retro),
 		ReactURL:     fmt.Sprintf("/d/%s/f/%s/react", box.ID, file.ID),
-		Reactions:    a.reactionViews(reactions),
+		Reactions:    reactionViews,
+		ReactionMore: reactionOverflowCount(reactionViews),
 		Reacted:      reacted,
 	}
 }
@@ -413,17 +417,25 @@ func (a *App) ReactToFile(w http.ResponseWriter, r *http.Request) {
 
 func (a *App) reactionViews(reactions []services.ReactionSummary) []reactionView {
 	views := make([]reactionView, 0, len(reactions))
-	for _, reaction := range reactions {
+	for index, reaction := range reactions {
 		views = append(views, reactionView{
 			EmojiID: reaction.EmojiID,
 			URL:     emojiURL(reaction.EmojiID),
 			Label:   emojiLabel(reaction.EmojiID),
 			Count:   reaction.Count,
+			Visible: index < 2,
 		})
 	}
 	return views
 }
 
+func reactionOverflowCount(reactions []reactionView) int {
+	if len(reactions) <= 2 {
+		return 0
+	}
+	return len(reactions) - 2
+}
+
 func (a *App) emojiTabs() ([]emojiTabView, error) {
 	root := a.emojiRoot()
 	entries, err := os.ReadDir(root)