Complete private authentication, server integrations and activity reporting

Add Fabric/Forge version builds and Paper integration, preserve permanent player identities across renames, harden session authorization, and surface privacy-conscious launcher/server activity in the panel.

integrations/common/src/main/java/net/scopenet/integration/Settings.java

@@ -0,0 +1,39 @@
+package net.scopenet.integration;
+
+import java.io.IOException;
+import java.io.Reader;
+import java.net.URI;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Properties;
+
+public record Settings(URI panel, String token) {
+    public Settings {
+        if (panel == null || panel.getHost() == null || panel.getRawUserInfo() != null
+                || panel.getRawQuery() != null || panel.getRawFragment() != null
+                || !("https".equals(panel.getScheme()) || "http".equals(panel.getScheme()))) {
+            throw new IllegalArgumentException("panel-url must be an HTTP(S) URL without credentials, query or fragment");
+        }
+        token = token == null ? "" : token.trim();
+        if (!token.matches("sn_[A-Za-z0-9]{40}")) {
+            throw new IllegalArgumentException("Set the server token from the panel's Servers page");
+        }
+    }
+
+    public static Settings of(String panel, String token) {
+        return new Settings(URI.create(panel.trim().replaceAll("/+$", "")), token);
+    }
+
+    public static Settings load(Path path) throws IOException {
+        if (!Files.exists(path)) {
+            Files.createDirectories(path.toAbsolutePath().getParent());
+            Files.writeString(path, "# SCOPENET server integration\npanel-url=https://panel.example.com\ntoken=\n", StandardCharsets.UTF_8);
+        }
+        Properties properties = new Properties();
+        try (Reader reader = Files.newBufferedReader(path, StandardCharsets.UTF_8)) {
+            properties.load(reader);
+        }
+        return of(properties.getProperty("panel-url", ""), properties.getProperty("token", ""));
+    }
+}