fix: delay boss notifications until reveal and animate hp bar colours

- Move bossVictory sound and notification from gameContext into BattleModal,
  fired at the 5.2s reveal timeout so the animation plays before the spoiler
- Replace CSS width transition with a setInterval tick (50ms steps over 5s)
  so bossHpPercent and partyHpPercent update incrementally during the animation
- Both bars now use a shared getHpColour helper: green >50%, yellow 25-50%,
  red <25%, causing colour to shift naturally as the bar visually drains

apps/web/src/context/gameContext.tsx

@@ -1175,17 +1175,6 @@ export const GameProvider = ({
                 return applyBossResult(previous, bossId, result);
               });
               setBattleResult({ bossName, result });
-              if (result.won) {
-                if (enableSoundsReference.current) {
-                  playSound("bossVictory");
-                }
-                if (enableNotificationsReference.current) {
-                  sendNotification(
-                    "⚔️ Boss Defeated!",
-                    `You defeated ${bossName}!`,
-                  );
-                }
-              }
             }).
             catch(() => {
 
@@ -1785,14 +1774,6 @@ export const GameProvider = ({
         return applyBossResult(previous, bossId, result);
       });
       setBattleResult({ bossName: boss.name, result: result });
-      if (result.won) {
-        if (enableSoundsReference.current) {
-          playSound("bossVictory");
-        }
-        if (enableNotificationsReference.current) {
-          sendNotification("⚔️ Boss Defeated!", `You defeated ${boss.name}!`);
-        }
-      }
     } catch {
       // Silently ignore — server errors shouldn't crash the UI
     }