feat: add daily login bonus system with streak tracking

Awards escalating gold rewards each consecutive day (Day 7 grants bonus
crystals). Streak resets on missed days; a week multiplier boosts all
rewards for longer streaks. Shows a modal on first daily load and
displays the current streak on the character sheet.

packages/types/src/index.ts

@@ -41,6 +41,7 @@ export type {
   LeaderboardCategory,
   LeaderboardEntry,
   LeaderboardResponse,
+  LoginBonusResult,
   LoadResponse,
   PrestigeRequest,
   PrestigeResponse,

packages/types/src/interfaces/Api.ts

@@ -21,6 +21,19 @@ export interface SaveResponse {
   signature?: string;
 }
 
+export interface LoginBonusResult {
+  /** Current login streak day count */
+  streak: number;
+  /** Gold awarded for today's login */
+  goldEarned: number;
+  /** Crystals awarded (day 7 bonus, scaled by week multiplier) */
+  crystalsEarned: number;
+  /** Day within the 7-day cycle (1–7) */
+  day: number;
+  /** Week number multiplier (week 1 = ×1, week 2 = ×2, …) */
+  weekMultiplier: number;
+}
+
 export interface LoadResponse {
   state: GameState;
   /** Offline gold earned since last save (server-calculated) */
@@ -31,6 +44,10 @@ export interface LoadResponse {
   offlineSeconds: number;
   /** HMAC-SHA256 signature of the loaded state — store and include in next save request */
   signature?: string;
+  /** Daily login bonus awarded on this load (null if already claimed today) */
+  loginBonus: LoginBonusResult | null;
+  /** Current login streak (always present) */
+  loginStreak: number;
 }
 
 export interface BossChallengeRequest {