feat: suppression boutique legacy + refonte achievements milestones Clickerz

- Suppression route /boutique + Boutique.jsx, BoutiqueCard.jsx, shop.json, scss associés
  (le GeneratorShop sidebar fait déjà le job)
- Refonte complète achievements : 27 milestones basés sur le GameState réel
  (paliers ressources, générateurs, prestige, évolution, easter eggs humour)
- Suppression ancien système JSON statique + AchievementsCard legacy
- Page achievements : unlocked/locked state-aware, compteur progression

Frontend/src/scss/components/achievementscard.scss

@@ -1,33 +0,0 @@
-.achievCardcontainer {
-  display: flex;
-  flex-direction: column;
-  align-items: center;
-  border: solid 0.05rem;
-  max-width: 250px;
-  border-radius: 1rem;
-  background-color: rgb(255, 255, 255);
-  margin-bottom: 1rem;
-  box-shadow: 1px 1px 10px 2px var(--color-grey);
-
-}
-
-.achievecardpicture {
-  width: 100%;
-  border-radius: 1rem 1rem 0 0;
-}
-
-.achievname {
-  font-size: 1.2rem;
-  margin-top: 0.2rem;
-  font-family: var(--font);
-  text-align: center;
-  color:rgb(29, 30, 30);
-}
-.achievdescription {
-  font-size: 1rem;
-  font-weight: 400;
-  color: var(--color-grey);
-  font-family: var(--font);
-  color:rgb(25, 25, 26);
-  padding: 1rem;
-}

Frontend/src/scss/components/boutiquecard.scss

@@ -1,76 +0,0 @@
-.shopcardcontainer {
-  display: flex;
-  flex-direction: column;
-  width: 300px;
-  min-height: 520px;
-  padding: 1rem;
-  border-radius: 1rem;
-  align-items: center;
-  box-sizing: border-box;
-  background-color: var(--color-white);
-
-  font-family: var(--font);
-
-  .shopcontainer {
-    width: 100%;
-    height: 100%;
-    display: flex;
-    flex-direction: column;
-    justify-content: space-between;
-    gap: 1rem;
-
-    .cardpicture {
-      width: 100%;
-      height: 300px;
-      padding: 3rem;
-      background-size: 50%;
-      background-position: center;
-      background-repeat: no-repeat;
-      border-radius: 10px;
-      background-color: var(--color-purple-light);
-      box-sizing: border-box;
-    }
-
-    .titlesection {
-      display: flex;
-      flex-direction: row;
-      justify-content: space-between;
-      margin-top: 1rem;
-
-      .itemname {
-        font-size: 1.2rem;
-        font-weight: 600;
-        color: var(--color-grey);
-      }
-
-      .price {
-        display: flex;
-        gap: 0.2rem;
-        font-size: 1rem;
-        font-weight: 400;
-        color: var(--color-grey);
-        .itemprice {
-          font-weight: 600;
-          color: var(--color-red-light);
-        }
-        .priceicon {
-          width: 22px;
-          height: 22px;
-          background-image: url("/svg/tadpole.svg");
-          background-size: contain;
-          background-position: center;
-          background-repeat: no-repeat;
-        }
-      }
-    }
-
-    .description {
-      font-size: 1rem;
-      font-weight: 400;
-      color: var(--color-grey);
-    }
-  }
-  .buttoncard {
-    width: 100%;
-  }
-}