feat: Windows NSIS installer, embedded icons, GUI auto-launch backend

- Add package/installer.nsi (Full/Server/Client) and toolchain.nsi
- Embed icon.ico (rounded corners) into homed.exe/waiter.exe via .syso
- GUI auto-launches homed.exe from parent dir (Windows only)
- GUI fallback connections.json from app resource dir
- Add initconfig command for config.db seeding
- Replace waiter rawmode* with raw_{unix,windows,other}.go
- Fix .gitignore: /homed instead of homed, add login.json
- Update icon.svg with rounded rect, new mascot.svg

cmd/gui/icon.svg

@@ -1,5 +1,5 @@
 <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 400 400" width="400" height="400">
-  <rect width="400" height="400" fill="#F8FAFC"/>
+  <rect width="400" height="400" rx="60" ry="60" fill="#F8FAFC"/>
 
   <g transform="translate(200,200)">
     <circle cx="0" cy="0" r="105" fill="none" stroke="#E2E8F0" stroke-width="2.5" stroke-dasharray="8,6"/>