Add setting to hide Anti-AFK stream indicator

[zortos293]

This PR adds a persisted user setting to hide the on-stream Anti-AFK indicator badge without changing Anti-AFK behavior or shortcut functionality. The setting defaults to true to preserve existing behavior.

Shared & Main:

• Add showAntiAfkIndicator: boolean to the Settings interface in src/shared/gfn.ts
• Add the field to src/main/settings.ts with default true and proper JSDoc comment

Renderer:

• Add showAntiAfkIndicator to initial settings state in src/renderer/src/App.tsx
• Pass the setting through to StreamView as a prop

Settings UI:

• Add toggle in Settings → Interface/Appearance section in src/renderer/src/components/SettingsPage.tsx
• Positioned alongside existing stream UI toggles (Hide Stream Overlay Buttons, Show Stats on Stream Launch)

Stream View:

• Update AntiAfkIndicator component to check both antiAfkEnabled and showAntiAfkIndicator before rendering
• Update MicrophoneIndicator and RecordingIndicator to use showAntiAfkIndicator for badge stacking logic
• Anti-AFK pulse behavior and shortcut toggling remain unchanged

Validation:

• Typecheck and build pass with no errors (npm run typecheck && npm run build)