feat: add daily challenges system

Three PST-midnight-resetting challenges generated deterministically per
day from click, boss, quest, and prestige types. Progress tracked
server-side for bosses and prestige, client-side for clicks and quests.
Crystal rewards awarded on completion and preserved through prestige resets.

apps/web/src/utils/dailyChallenges.ts

@@ -0,0 +1,32 @@
+import type { DailyChallengeState, DailyChallengeType } from "@elysium/types";
+
+/**
+ * Increments progress for daily challenges matching the given type.
+ * Returns the updated challenge state and any crystals awarded for newly-completed challenges.
+ *
+ * Note: challenge generation and daily resets are handled server-side only.
+ * This utility is purely for client-side progress tracking.
+ */
+export const updateChallengeProgress = (
+  challengeState: DailyChallengeState,
+  type: DailyChallengeType,
+  amount: number,
+): { updatedChallenges: DailyChallengeState; crystalsAwarded: number } => {
+  let crystalsAwarded = 0;
+
+  const updatedChallenges: DailyChallengeState = {
+    ...challengeState,
+    challenges: challengeState.challenges.map((challenge) => {
+      if (challenge.type !== type || challenge.completed) return challenge;
+
+      const newProgress = Math.min(challenge.progress + amount, challenge.target);
+      const nowCompleted = newProgress >= challenge.target;
+
+      if (nowCompleted) crystalsAwarded += challenge.rewardCrystals;
+
+      return { ...challenge, progress: newProgress, completed: nowCompleted };
+    }),
+  };
+
+  return { updatedChallenges, crystalsAwarded };
+};