Begin work on biergarten data generator pipeline

pipeline/includes/json_loader.h

@@ -0,0 +1,13 @@
+#pragma once
+
+#include "database.h"
+#include "stream_parser.h"
+#include "work_queue.h"
+#include <string>
+
+/// @brief Loads world-city JSON data into SQLite through streaming parsing.
+class JsonLoader {
+public:
+  /// @brief Parses a JSON file and writes country/state/city rows into db.
+  static void LoadWorldCities(const std::string &jsonPath, SqliteDatabase &db);
+};