Add launcher engine (scopenet-core) and admin panel server

- scopenet-shared: wire types for branding, auth, instances, manifests
- scopenet-core: Mojang versions/libraries/assets, automatic Java runtimes,
  Fabric/Quilt/Forge/NeoForge installation, file sync, launch command
  builder, Microsoft auth, servers.dat injection, server list ping
- scopenet-panel: Axum + SQLite admin API with JWT auth, users/groups,
  branding, settings, instances, Modrinth/CurseForge/zip import, file
  hosting and launch stats

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

crates/core/src/lib.rs

@@ -0,0 +1,28 @@
+//! ScopeNet launcher engine.
+//!
+//! The Tauri app is a thin UI shell around this crate: everything that
+//! downloads, installs or launches Minecraft lives here so it can be unit
+//! tested without a window.
+
+pub mod assets;
+pub mod http;
+pub mod install;
+pub mod java;
+pub mod launch;
+pub mod libraries;
+pub mod loaders;
+pub mod maven;
+pub mod meta;
+pub mod msa;
+pub mod options;
+pub mod paths;
+pub mod ping;
+pub mod progress;
+pub mod rules;
+pub mod servers_dat;
+pub mod sync;
+pub mod sys;
+pub mod version;
+
+pub use paths::Layout;
+pub use progress::{Event, Reporter, Stage};