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/maven.rs

@@ -0,0 +1,74 @@
+/// A Maven coordinate: `group:artifact:version[:classifier][@ext]`.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct Coord {
+    pub group: String,
+    pub artifact: String,
+    pub version: String,
+    pub classifier: Option<String>,
+    pub ext: String,
+}
+
+impl Coord {
+    pub fn parse(s: &str) -> Option<Self> {
+        let s = s.trim().trim_start_matches('[').trim_end_matches(']');
+        let (main, ext) = match s.split_once('@') {
+            Some((m, e)) => (m, e.to_string()),
+            None => (s, "jar".to_string()),
+        };
+        let parts: Vec<&str> = main.split(':').collect();
+        if parts.len() < 3 {
+            return None;
+        }
+        Some(Self {
+            group: parts[0].into(),
+            artifact: parts[1].into(),
+            version: parts[2].into(),
+            classifier: parts.get(3).map(|c| c.to_string()),
+            ext,
+        })
+    }
+
+    /// Relative repository path (`/`-separated).
+    pub fn path(&self) -> String {
+        let classifier = self.classifier.as_ref().map(|c| format!("-{c}")).unwrap_or_default();
+        format!(
+            "{}/{}/{}/{}-{}{}.{}",
+            self.group.replace('.', "/"),
+            self.artifact,
+            self.version,
+            self.artifact,
+            self.version,
+            classifier,
+            self.ext
+        )
+    }
+
+    /// Identity used to de-duplicate libraries (version-less).
+    pub fn key(&self) -> String {
+        match &self.classifier {
+            Some(c) => format!("{}:{}:{}", self.group, self.artifact, c),
+            None => format!("{}:{}", self.group, self.artifact),
+        }
+    }
+
+    pub fn with_classifier(&self, classifier: &str) -> Self {
+        Self { classifier: Some(classifier.to_string()), ..self.clone() }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn parses_coords() {
+        let c = Coord::parse("net.fabricmc:fabric-loader:0.16.9").unwrap();
+        assert_eq!(c.path(), "net/fabricmc/fabric-loader/0.16.9/fabric-loader-0.16.9.jar");
+        let c = Coord::parse("de.oceanlabs.mcp:mcp_config:1.20.1-20230612.114412@zip").unwrap();
+        assert_eq!(c.path(), "de/oceanlabs/mcp/mcp_config/1.20.1-20230612.114412/mcp_config-1.20.1-20230612.114412.zip");
+        let c = Coord::parse("[net.minecraft:client:1.20.1-20230612.114412:slim]").unwrap();
+        assert_eq!(c.path(), "net/minecraft/client/1.20.1-20230612.114412/client-1.20.1-20230612.114412-slim.jar");
+        assert_eq!(c.key(), "net.minecraft:client:slim");
+        assert!(Coord::parse("nope").is_none());
+    }
+}