fix: onboarding "Set Password" label, reboot sequence, initramfs noise

- OnboardingDone: "Go to Login" → "Set Password" with context text
- Reboot: lazy-unmount live FS before USB removal prompt, suppress
  kernel SquashFS messages, auto-reboot after 10s countdown
- Initramfs: filter "Possible missing firmware" warnings (cosmetic)
- ISOLINUX: menu centered at bottom (VSHIFT 18, HSHIFT 32, WIDTH 18)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

neode-ui/src/views/OnboardingDone.vue

@@ -42,12 +42,13 @@
           </div>
         </div>
 
-        <!-- Go to Login Button -->
+        <!-- Set Password Button -->
+        <p class="text-xs text-white/50 mb-3">You'll create your node password next</p>
         <button
           @click="goToLogin"
           class="path-action-button path-action-button--continue mx-auto"
         >
-          Go to Login
+          Set Password
         </button>
       </div>
     </div>