fix: particule clic affiche le vrai gain (clickMult × prestigeMult × treeMult)

Ajout getClickGain() dans economy.ts — utilisé par la particule de feedback
et le cockpit header "Ponte". Avant : affichait toujours +1.

Frontend/src/pages/Home.jsx

@@ -4,6 +4,7 @@ import { useEffect, useCallback } from "react";
 
 import { useGameStore } from "../store/useGameStore";
 import { formatNumber } from "../utils/formatNumber";
+import { getClickGain } from "../core/economy";
 import { GeneratorShop } from "../components/GeneratorShop";
 import { PrestigePanel } from "../components/PrestigePanel";
 import { EvolutionTree } from "../components/EvolutionTree";
@@ -17,19 +18,20 @@ export default function Home() {
   const [toggleRain] = useOutletContext();
   const click = useGameStore((s) => s.click);
   const resources = useGameStore((s) => s.state.resources);
-  const clickMultiplier = useGameStore((s) => s.state.clickMultiplier);
+  const state = useGameStore((s) => s.state);
+  const clickGain = getClickGain(state);
 
   const createParticle = useCallback((clientX, clientY) => {
     const particle = document.createElement("span");
     particle.className = "click-particle";
-    particle.textContent = `+${formatNumber(clickMultiplier)}`;
+    particle.textContent = `+${formatNumber(clickGain)}`;
     particle.style.left = `${clientX}px`;
     particle.style.top = `${clientY}px`;
     document.body.appendChild(particle);
     setTimeout(() => {
       if (particle.parentNode) particle.parentNode.removeChild(particle);
     }, 800);
-  }, [clickMultiplier]);
+  }, [clickGain]);
 
   const handleIncrement = useCallback((e) => {
     click();