Add list styles: Podium, Spotlight, Grid, List

- Each list picks a style in List settings (new lists default to Podium);
  existing lists keep Grid or List
- Podium: top 3 on medal-colored steps (#1 center and raised), the rest
  behind a native <details> "Show N more"; stacks #1 over #2/#3 on phones
- Spotlight: #1 as a feature card (art, why-note or description, play
  button), the rest as a numbered list
- Visitors can switch styles on a list page (?style=), preserved across
  pages; later pages fall back to a plain list since they don't start at #1
- Entries' detail data now lives on a wrapper per list, so featured and
  collapsed entries all open the detail view

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/store/lists.go

@@ -24,7 +24,7 @@ type List struct {
 	MaxItems    int    `json:"maxItems"`
 	Position    int    `json:"position"`
 	Visible     bool   `json:"visible"`
-	Layout      string `json:"layout"` // "grid" or "rows"
+	Layout      string `json:"layout"` // a ListStyles key, e.g. "podium"
 	Art         string `json:"art"`    // "", "poster" or "square"; "" = category default
 	ItemCount   int    `json:"itemCount"`
 	UpdatedAt   int64  `json:"updatedAt"`
@@ -97,8 +97,8 @@ func (l *List) normalize() error {
 	if l.MaxItems < 1 || l.MaxItems > MaxListSize {
 		return invalid("List size must be between 1 and %d", MaxListSize)
 	}
-	if l.Layout != "rows" {
-		l.Layout = "grid"
+	if _, ok := StyleByKey(l.Layout); !ok {
+		l.Layout = DefaultStyle
 	}
 	if l.Art != "poster" && l.Art != "square" {
 		l.Art = ""
@@ -245,3 +245,29 @@ func (l List) Aspect() string {
 	c, _ := CategoryByKey(l.Category)
 	return c.Aspect
 }
+
+// ListStyle is a way of presenting a ranked list.
+type ListStyle struct {
+	Key         string `json:"key"`
+	Label       string `json:"label"`
+	Icon        string `json:"icon"`
+	Description string `json:"description"`
+}
+
+var ListStyles = []ListStyle{
+	{"podium", "Podium", "podium", "Top 3 on a medal podium, the rest behind “Show more”."},
+	{"spotlight", "Spotlight", "spotlight", "#1 as a big feature, the rest as a ranked list."},
+	{"grid", "Grid", "grid", "Every entry as artwork in a grid."},
+	{"rows", "List", "rows", "A compact numbered list with notes."},
+}
+
+const DefaultStyle = "podium"
+
+func StyleByKey(key string) (ListStyle, bool) {
+	for _, s := range ListStyles {
+		if s.Key == key {
+			return s, true
+		}
+	}
+	return ListStyle{}, false
+}