feat: animation 30 jours en demi-semaines (3.5j, ~9 frames)

Remplace les frames hebdomadaires (5 frames) par des demi-semaines
(3.5 jours, ~9-10 frames) pour une animation plus fluide sur 30 jours.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/hooks/useAnimation.ts

@@ -39,20 +39,19 @@ function buildFrames(periodDays: number): TimeFrame[] {
     });
   }
 
-  // 30 days → weekly frames
+  // 30 days → half-week frames (3.5 days ≈ 9–10 frames)
+  const HALF_WEEK = 3.5 * 86_400_000;
   const frames: TimeFrame[] = [];
   let cursor = start;
-  let week = 1;
   while (cursor < now) {
     const from = cursor;
-    const to = Math.min(cursor + 7 * 86_400_000, now);
+    const to = Math.min(cursor + HALF_WEEK, now);
     frames.push({
-      label: `Semaine ${week} · ${fmt(from, { day: 'numeric', month: 'short' })} – ${fmt(to - 1, { day: 'numeric', month: 'short' })}`,
+      label: `${fmt(from, { day: 'numeric', month: 'short' })} – ${fmt(to - 1, { day: 'numeric', month: 'short' })}`,
       from,
       to,
     });
     cursor = to;
-    week++;
   }
   return frames;
 }