feat: container orchestration, branding overhaul, onboarding logging

Container orchestration:
- Health monitor with crash recovery and auto-restart
- Doctor service (periodic health checks via systemd timer)
- Reconcile service (desired-state convergence)
- Stack-aware install/uninstall with dependency tracking

Branding:
- Custom GRUB background (designer artwork, 1024x768)
- ISOLINUX boot menu: centered, orange accents, clean labels
- Terminal banners: adaptive width, basic ANSI colors, fits 80-col
- Removed auto-generated splash scripts (designer provides assets)
- GRUB theme: lowercase branding

Frontend:
- 401 handler clears localStorage immediately (prevents cascade)

Backend:
- Onboarding/auth logging ([onboarding] tag in journalctl)
- Cookie Secure flag logging for debugging HTTP/HTTPS issues

ISO fixes:
- Install log saved before unmount (was silently failing)

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

image-recipe/branding/grub-theme/theme.txt

@@ -23,7 +23,7 @@ desktop-image: "background.png"
     left = 25%
     top = 20%
     width = 50%
-    text = "A R C H I P E L A G O"
+    text = "a r c h i p e l a g o"
     color = "#f7931a"
     align = "center"
 }
@@ -32,7 +32,7 @@ desktop-image: "background.png"
     left = 25%
     top = 28%
     width = 50%
-    text = "Bitcoin Node OS"
+    text = "bitcoin node os"
     color = "#888888"
     align = "center"
 }
@@ -41,7 +41,7 @@ desktop-image: "background.png"
     left = 25%
     top = 90%
     width = 50%
-    text = "Use arrow keys to select, Enter to boot"
+    text = "use arrow keys to select, enter to boot"
     color = "#555555"
     align = "center"
 }