feat: add in-game sound effects and browser notifications (#27)

Adds Web Audio API sound effects and browser notifications for key game
events: achievement unlocked, quest completed, quest failed, boss
defeated, prestige, transcendence, and apotheosis. Both features are
toggled via profile settings, with notification permission requested
on first enable.

packages/types/src/interfaces/profileSettings.ts

@@ -38,10 +38,22 @@ interface ProfileSettings {
    * Whether this player appears on the public leaderboards.
    */
   showOnLeaderboards: boolean;
+
+  /**
+   * Whether in-game sound effects are enabled.
+   */
+  enableSounds: boolean;
+
+  /**
+   * Whether browser system notifications are enabled.
+   */
+  enableNotifications: boolean;
 }
 
 // eslint-disable-next-line @typescript-eslint/naming-convention -- intentional constant name
 const DEFAULT_PROFILE_SETTINGS: ProfileSettings = {
+  enableNotifications:              false,
+  enableSounds:                     false,
   numberFormat:                     "suffix",
   showAchievementsUnlocked:         true,
   showAdventurersRecruited:         true,

packages/types/test/profileSettings.spec.ts

@@ -20,6 +20,8 @@ describe("DEFAULT_PROFILE_SETTINGS", () => {
     expect(DEFAULT_PROFILE_SETTINGS.showAdventurersRecruited).toBe(true);
     expect(DEFAULT_PROFILE_SETTINGS.showAchievementsUnlocked).toBe(true);
     expect(DEFAULT_PROFILE_SETTINGS.showOnLeaderboards).toBe(true);
+    expect(DEFAULT_PROFILE_SETTINGS.enableSounds).toBe(false);
+    expect(DEFAULT_PROFILE_SETTINGS.enableNotifications).toBe(false);
   });
 
   it("defaults numberFormat to suffix", () => {