feat(porttracker): add DB access layer and init command

Add Database.cs with SQLite connection management and helper methods
(Execute, ExecuteScalar, Query), Schema.cs for schema initialization,
and replace default Program.cs with System.CommandLine v3 CLI featuring
global --db/--schema options and an init command.

tools/NatsNet.PortTracker/Data/Schema.cs

@@ -0,0 +1,10 @@
+namespace NatsNet.PortTracker.Data;
+
+public static class Schema
+{
+    public static void Initialize(Database db, string schemaPath)
+    {
+        var sql = File.ReadAllText(schemaPath);
+        db.Execute(sql);
+    }
+}