revert: restore automatic WebAuthn authentication without manual button

**Motivations :**
- Remove manual authentication button as requested by user
- Restore automatic WebAuthn triggering like before
- Maintain seamless user experience without manual intervention
- Keep WebAuthn security while ensuring automatic flow

**Modifications :**
- Removed manual authentication button and click handler
- Restored automatic WebAuthn triggering in handleMainPairing()
- Simplified authentication flow to be automatic on page load
- Maintained proper error handling and user feedback
- Kept spinner and status messages for user feedback

**Pages affectées :**
- src/pages/home/home.ts: Restored automatic WebAuthn authentication flow

src/pages/home/home.ts

@@ -484,7 +484,7 @@ async function handleDeleteAccount(): Promise<void> {
     }
 
     // Get services
-    const service = await Services.getInstance();
+  const service = await Services.getInstance();
     const { secureCredentialsService } = await import('../../services/secure-credentials.service');
 
     // Delete all credentials