feat: support every song difficulty including Easy and Normal

src/lib/models/analysis-history.ts

@@ -1,7 +1,8 @@
+import type { DifficultyKey } from '../data/difficulty.ts';
 import type { CooldownReduction, ExactOptimizationResult } from '../engine/types.ts';
 
 export type AnalysisSettings = {
-  songId: string; difficulty: 'hard' | 'expert'; cardIds: string[]; awakenings: number[];
+  songId: string; difficulty: DifficultyKey; cardIds: string[]; awakenings: number[];
   fixedCooldownReductions?: (CooldownReduction | null)[];
   allBlueNodes?: boolean[]; generationBonusOverrides?: (number | null)[];
   songScoreBonusOverride?: number | null; leaderCharacterId: string; leaderOutfitCardId: string;