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.

web/src/types.ts

@@ -89,6 +89,7 @@ export interface GameView {
   pending?: PendingTrade
   battle?: BattleResult
   winnerSeat: number
+  debug?: boolean // server DEBUG mode: unlocks the buy-any-card panel
 }
 
 export type ClientMessage =
@@ -99,6 +100,7 @@ export type ClientMessage =
   | { type: 'pass' }
   | { type: 'arrange'; order: string[] }
   | { type: 'ready' }
+  | { type: 'debugAdd'; name: string }
 
 export interface Session {
   gameId: string