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/Cargo.toml

@@ -0,0 +1,26 @@
+[package]
+name = "scopenet-core"
+description = "Minecraft install / launch engine used by the ScopeNet launcher (and meta lookups in the panel)"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+
+[dependencies]
+scopenet-shared.workspace = true
+anyhow.workspace = true
+serde.workspace = true
+serde_json.workspace = true
+tokio.workspace = true
+reqwest.workspace = true
+futures.workspace = true
+sha1.workspace = true
+hex.workspace = true
+zip.workspace = true
+tracing.workspace = true
+fastnbt = "2"
+
+[target.'cfg(windows)'.dependencies]
+windows-sys = { version = "0.59", features = ["Win32_System_SystemInformation"] }
+
+[dev-dependencies]
+tempfile = "3"