Add DEBUG-gated panel to buy any card in the shop

When the server's DEBUG env var is on, expose a card catalog endpoint
and a collapsible client panel that drops any pet or food straight into
your deck (free, off-turn). Gated server-side so it is inert in normal
play.

internal/game/cards.go

@@ -519,6 +519,60 @@ func (g *Game) buildShopDecks() {
 	}
 }
 
+// Catalog returns one representative card for every pet and food in the game,
+// tier by tier, for the debug "buy any card" panel. IDs are name-based
+// placeholders (not real instances); pets use their first printed suit.
+func Catalog() []Card {
+	var cards []Card
+	for tierIdx := range petTiers {
+		for _, t := range petTiers[tierIdx] {
+			suit := SuitRed
+			if len(t.Suits) > 0 {
+				suit = t.Suits[0]
+			}
+			cards = append(cards, Card{
+				ID: "pet-" + t.Name, Kind: KindPet, Name: t.Name, Tier: tierIdx + 1,
+				Power: t.Power, Suit: suit, Effects: t.Effects, EffectText: t.EffectText,
+			})
+		}
+		for _, f := range foodTiers[tierIdx] {
+			cards = append(cards, Card{
+				ID: "food-" + f.Name, Kind: KindFood, Name: f.Name, Tier: tierIdx + 1,
+				Food: f.Food, Perk: f.Perk, Effects: f.Effects, EffectText: f.EffectText,
+			})
+		}
+	}
+	return cards
+}
+
+// cardByName mints a fresh instance of the named pet or food from its
+// template (pets take their first printed suit). Returns false if unknown.
+func (g *Game) cardByName(name string) (Card, bool) {
+	for tierIdx := range petTiers {
+		for _, t := range petTiers[tierIdx] {
+			if t.Name == name {
+				suit := SuitRed
+				if len(t.Suits) > 0 {
+					suit = t.Suits[0]
+				}
+				return Card{
+					ID: g.newCardID(), Kind: KindPet, Name: t.Name, Tier: tierIdx + 1,
+					Power: t.Power, Suit: suit, Effects: t.Effects, EffectText: t.EffectText,
+				}, true
+			}
+		}
+		for _, f := range foodTiers[tierIdx] {
+			if f.Name == name {
+				return Card{
+					ID: g.newCardID(), Kind: KindFood, Name: f.Name, Tier: tierIdx + 1,
+					Food: f.Food, Perk: f.Perk, Effects: f.Effects, EffectText: f.EffectText,
+				}, true
+			}
+		}
+	}
+	return Card{}, false
+}
+
 // newApple mints an apple food card. Apples are temporary: they vanish from
 // the deck after the next battle.
 func (g *Game) newApple() Card {