Refactor large files into modular components

- Refactored page.tsx (613→252 lines) with GameOverScreen and LeftPanel extracted
- Refactored StatsTab.tsx (584→92 lines) with section components
- Refactored SkillsTab.tsx (434→54 lines) with sub-components
- Created modular structure for GameContext, LootInventory, and other components
- All extracted components organized into feature directories

src/lib/game/stores/gameHooks.ts

@@ -0,0 +1,13 @@
+import { useGameStore } from './gameStore';
+import { TICK_MS } from '../constants';
+
+export function useGameLoop() {
+  const tick = useGameStore((s) => s.tick);
+
+  return {
+    start: () => {
+      const interval = setInterval(tick, TICK_MS);
+      return () => clearInterval(interval);
+    },
+  };
+}