feat: Add character names to scenarios and UI

Introduces `characterName` to the `Scenario` type, enabling AI personas to be explicitly named. This change also updates the `ScenarioCard` component to display the character name and adds foundational support for potential future scenario deletion functionality. The README has been updated with a new AI Studio link.

types.ts

@@ -8,12 +8,14 @@ export interface Scenario {
   systemInstruction: string;
   initialMessage: string;
   cbtFocus: string[];
+  characterName: string;
 }
 
 export interface UserSettings {
   voiceName: 'Puck' | 'Charon' | 'Kore' | 'Fenrir' | 'Zephyr';
   vocalStyle: string;
   genderPreference: 'Male' | 'Female' | 'Neutral';
+  preferredAudioDeviceId?: string;
 }
 
 export interface Message {