feat(sprint1-step5): migration Tailwind v4 + Zustand — suppression WildCoinContext

- Install tailwindcss @tailwindcss/vite zustand
- useGameStore.ts : Zustand store wrappant economy.ts (tick, click, buy, prestige, buyNode, loadFromServer)
- GameTick.tsx : composant timer 1s
- GeneratorShop.tsx : boutique générateurs Tailwind (remplace Amelioration.jsx)
- EvolutionTree, PrestigePanel, MilestoneBar : rewrite Zustand + Tailwind
- Hud.jsx : rewrite Zustand + Tailwind (suppression Hud.scss)
- BoutiqueCard, Achievements : migrés vers Zustand
- Supprimé : WildCoin/ (4 fichiers), timer/Timer.jsx, useEconomy.ts, Hud.scss
- WildCoinProvider retiré de main.jsx

Frontend/src/components/GeneratorShop.tsx

@@ -0,0 +1,51 @@
+// GeneratorShop.tsx — Boutique de générateurs (economy.ts)
+// Remplace Amelioration.jsx (legacy WildCoinContext)
+
+import { useGameStore } from "../store/useGameStore";
+import { formatNumber } from "../utils/formatNumber";
+
+export function GeneratorShop() {
+  const generators = useGameStore((s) => s.state.generators);
+  const resources = useGameStore((s) => s.state.resources);
+  const buy = useGameStore((s) => s.buy);
+  const generatorCost = useGameStore((s) => s.generatorCost);
+
+  return (
+    <div className="flex flex-col gap-3 p-4 rounded-xl bg-gray-900/80 backdrop-blur-sm max-w-md w-full">
+      <h2 className="text-lg font-bold text-white">Générateurs</h2>
+      {generators.map((gen) => {
+        const cost = generatorCost(gen);
+        const canAfford = resources >= cost;
+
+        return (
+          <div
+            key={gen.id}
+            className={`flex items-center justify-between gap-3 p-3 rounded-lg border transition-colors ${
+              canAfford
+                ? "border-emerald-500/50 bg-emerald-950/30 hover:bg-emerald-950/50"
+                : "border-gray-700/50 bg-gray-800/30 opacity-60"
+            }`}
+          >
+            <div className="flex flex-col min-w-0">
+              <span className="text-white font-semibold text-sm">{gen.name}</span>
+              <span className="text-gray-400 text-xs">
+                +{gen.baseProduction}/s &middot; x{gen.owned}
+              </span>
+            </div>
+            <button
+              onClick={() => buy(gen.id)}
+              disabled={!canAfford}
+              className={`shrink-0 px-3 py-1.5 rounded-md text-sm font-medium transition-colors cursor-pointer ${
+                canAfford
+                  ? "bg-emerald-600 hover:bg-emerald-500 text-white"
+                  : "bg-gray-700 text-gray-500 cursor-not-allowed"
+              }`}
+            >
+              {formatNumber(cost)}
+            </button>
+          </div>
+        );
+      })}
+    </div>
+  );
+}