feat: Sprint 3 — Prestige Loop endless

- Migration saves: saveVersion pattern + migrateSave lazy (v1→v2)
- Formule ADN rebalancée: log10 + clamp min 1 + cap bonus ×4
- Prestige Experience: modal fullscreen, preview ADN, stats run, best run
- Arbre V2: 25 nœuds, 3 capstones, post-capstones repeatables (scaling par tranche)
- Convergence évolutif Alpha→Omega (tier system)
- Reset arbre: 1 gratuit/prestige, payant linéaire au-delà
- Milestones prestige: 8 paliers (1→100), cosmétiques exclusifs, bonus gameplay
- balance.ts: constantes centralisées pour playtest
- 136 tests green, 0 regression

Frontend/src/components/MilestonesPanel.tsx

@@ -0,0 +1,89 @@
+// MilestonesPanel.tsx — Paliers de prestige (Sprint 3)
+// Progress bar vers le prochain milestone, claim button, preview reward
+
+import { useGameStore } from "../store/useGameStore";
+import { getClaimableMilestones, getNextMilestone } from "../core/economy";
+import { PRESTIGE_MILESTONES } from "../data/prestigeMilestones";
+
+export function MilestonesPanel() {
+  const state = useGameStore((s) => s.state);
+  const claim = useGameStore((s) => s.claimMilestone);
+
+  if (state.prestigeCount < 1) return null;
+
+  const claimable = getClaimableMilestones(state);
+  const nextMilestone = getNextMilestone(state);
+  const totalClaimed = state.claimedMilestones.length;
+
+  return (
+    <div className="gp">
+      <div className="flex justify-between items-center">
+        <span className="gp-title">Milestones</span>
+        <span className="gp-label">{totalClaimed}/{PRESTIGE_MILESTONES.length}</span>
+      </div>
+
+      {/* Claimable milestones */}
+      {claimable.length > 0 && (
+        <div className="flex flex-col gap-1.5">
+          {claimable.map((m) => (
+            <div key={m.id} className="gp-row gp-row--evolution border-purple-400/30!">
+              <div className="flex flex-col min-w-0">
+                <span className="gp-value text-[0.7rem]!">{m.name}</span>
+                <span className="gp-label">{m.reward.label}</span>
+              </div>
+              <button
+                onClick={() => claim(m.id)}
+                className="gp-btn gp-btn--buy"
+              >
+                Claim
+              </button>
+            </div>
+          ))}
+        </div>
+      )}
+
+      {/* Progress vers le prochain milestone */}
+      {nextMilestone && (
+        <div className="flex flex-col gap-1">
+          <div className="flex justify-between">
+            <span className="gp-label">Prochain : {nextMilestone.name}</span>
+            <span className="gp-label">
+              {state.prestigeCount}/{nextMilestone.threshold}
+            </span>
+          </div>
+          <div className="gp-progress">
+            <div
+              className="gp-progress-fill bg-gradient-to-r from-purple-600 to-purple-400"
+              style={{
+                width: `${Math.min((state.prestigeCount / nextMilestone.threshold) * 100, 100).toFixed(1)}%`,
+              }}
+            />
+          </div>
+          <span className="gp-label">{nextMilestone.reward.label}</span>
+        </div>
+      )}
+
+      {/* Tous les milestones réclamés */}
+      {!nextMilestone && claimable.length === 0 && (
+        <span className="gp-label text-center gp-accent-purple">
+          Tous les milestones reclames !
+        </span>
+      )}
+
+      {/* Liste compacte des milestones passés */}
+      {totalClaimed > 0 && claimable.length === 0 && (
+        <div className="flex flex-wrap gap-1 mt-1">
+          {PRESTIGE_MILESTONES.filter((m) => state.claimedMilestones.includes(m.id)).map((m) => (
+            <span
+              key={m.id}
+              className="gp-label text-[0.55rem]! px-1.5 py-0.5 rounded bg-purple-500/10 border border-purple-500/20"
+              title={`${m.name} — ${m.description}`}
+            >
+              {m.threshold}
+            </span>
+          ))}
+        </div>
+      )}
+    </div>
+  );
+}