Restyle to a clean, flat look and rename brand to SCOPENET

- Brand is now SCOPENET everywhere (defaults, UI, installer, docs)
- Launcher: solid backgrounds (no animated orbs/grain), flat Play button
  without gradient/shine/glow, quieter rail with a simple active
  indicator, smaller type scale, Inter as default font, glass off by
  default, restyled sliders
- Panel: same flat treatment; live preview mirrors the new launcher
- New flat scope-reticle logo and app icons
- Calmer default palette
- Fix: lock the shared cargo cache in the Docker build (amd64/arm64 raced)
- Fix: Windows-only clippy lint in sys.rs

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011ARcGWxLx21FwXJ3yfGriS

README.md

@@ -2,7 +2,7 @@
 
 <img src="launcher/src-tauri/icons/128x128.png" width="96" alt="" />
 
-# ScopeNet
+# SCOPENET
 
 **A fast, fully customisable Minecraft launcher — and the self-hosted admin panel that controls it.**
 
@@ -117,5 +117,5 @@ docker-compose.yml Panel deployment
 
 ## Notes
 
-- Minecraft is a trademark of Mojang Studios. ScopeNet is not affiliated with Mojang or Microsoft. Offline mode is intended for your own community servers.
+- Minecraft is a trademark of Mojang Studios. SCOPENET is not affiliated with Mojang or Microsoft. Offline mode is intended for your own community servers.
 - No license has been chosen yet — add a `LICENSE` file before distributing.