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/server/render.go

@@ -103,6 +103,17 @@ var funcs = template.FuncMap{
 	},
 	"add":       func(a, b int) int { return a + b },
 	"hasPrefix": strings.HasPrefix,
+	// first and after split a ranked list: the podium/spotlight entries and
+	// everything below them.
+	"first": func(n int, items []ItemView) []ItemView { return items[:min(n, len(items))] },
+	"after": func(n int, items []ItemView) []ItemView { return items[min(n, len(items)):] },
+	// flatLayout is how a style shows entries that aren't featured.
+	"flatLayout": func(style string) string {
+		if style == "grid" {
+			return "grid"
+		}
+		return "rows"
+	},
 	// dict builds a map for passing several values to a partial.
 	"dict": func(kv ...any) map[string]any {
 		m := map[string]any{}