Update Biometric Login view to new design system

**Description:**
Update `BiometricLoginView.tsx` to replace any blue color references (`text-[#2563EB]`) with gray equivalents (`text-gray-900`). Keep all functionality unchanged.

**Acceptance Criteria:**
- [ ] Blue text colors replaced with `text-gray-900`
- [ ] No functional changes

**File(s):** `frontend/components/auth/BiometricLoginView.tsx`
