Add Docker image, Compose, CI/CD workflows and docs

- Multi-arch (amd64/arm64) panel image: static musl binary on scratch,
  cross-compiled with cargo-zigbuild (no QEMU), non-root, healthcheck
- docker-compose.yml + .env.example for one-command deployment
- CI: fmt, clippy, tests, web type-checks, Windows launcher build,
  real-network installs of vanilla/Fabric/Quilt/Forge/NeoForge,
  Docker build
- Release: Windows NSIS installer with baked-in panel URL, GHCR image
  push and GitHub release (tag push or manual dispatch)
- README, admin guide, Microsoft auth setup, architecture, development
- rustfmt config and formatting pass

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

crates/core/src/sync.rs

@@ -76,11 +76,7 @@ pub async fn sync(
             continue;
         };
         wanted.insert(f.path.replace('\\', "/"));
-        let ok = if changed {
-            http::file_ok(&dest, Some(&f.sha1), Some(f.size), true)
-        } else {
-            dest.exists()
-        };
+        let ok = if changed { http::file_ok(&dest, Some(&f.sha1), Some(f.size), true) } else { dest.exists() };
         if !ok {
             downloads.push(Download::new(resolve_url(panel_base, &f.url), dest, Some(f.sha1.clone()), Some(f.size)));
         }