feat(boot): set 1920x1080 resolution for framebuffer and GRUB

- Add video=1920x1080 to kernel cmdline (sets fbdev to Full HD)
- Update GRUB gfxmode to 1920x1080 (fallback to 1280x1024,auto)
- Add Xorg Monitor section with 1920x1080 Modeline and preferred mode

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

iso/overlay/etc/X11/xorg.conf.d/10-fbdev.conf

@@ -4,7 +4,19 @@ Section "Device"
     Option      "fbdev" "/dev/fb0"
 EndSection
 
+Section "Monitor"
+    Identifier  "monitor0"
+    Modeline    "1920x1080" 148.50 1920 2008 2052 2200 1080 1084 1089 1125 +hsync +vsync
+    Option      "PreferredMode" "1920x1080"
+EndSection
+
 Section "Screen"
     Identifier  "screen0"
     Device      "fbdev"
+    Monitor     "monitor0"
+    DefaultDepth 24
+    SubSection "Display"
+        Depth   24
+        Modes   "1920x1080" "1280x1024" "1024x768"
+    EndSubSection
 EndSection