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

panel/server/Cargo.toml

@@ -0,0 +1,35 @@
+[package]
+name = "scopenet-panel"
+description = "ScopeNet admin panel: manages instances, branding and players for the launcher"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+
+[dependencies]
+scopenet-shared.workspace = true
+scopenet-core.workspace = true
+anyhow.workspace = true
+thiserror.workspace = true
+serde.workspace = true
+serde_json.workspace = true
+tokio.workspace = true
+reqwest.workspace = true
+futures.workspace = true
+sha1.workspace = true
+hex.workspace = true
+uuid.workspace = true
+zip.workspace = true
+tracing.workspace = true
+chrono.workspace = true
+rand.workspace = true
+axum = { version = "0.8", features = ["multipart", "macros"] }
+tower = { version = "0.5", features = ["util"] }
+tower-http = { version = "0.6", features = ["fs", "trace", "compression-gzip", "set-header"] }
+tracing-subscriber = { version = "0.3", features = ["env-filter", "fmt"] }
+sqlx = { version = "0.8", default-features = false, features = ["runtime-tokio", "sqlite", "derive"] }
+argon2 = "0.5"
+jsonwebtoken = "9"
+percent-encoding = "2"
+
+[dev-dependencies]
+tempfile = "3"