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

crates/shared/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "scopenet-shared"
-description = "Types shared between the ScopeNet launcher and admin panel"
+description = "Types shared between the SCOPENET launcher and admin panel"
 version.workspace = true
 edition.workspace = true