docs(new): clarify project config initialization in generated app README

Author: GaspardKirira

src/commands/NewCommand.cpp

@@ -823,14 +823,55 @@ int main()
   static std::string make_readme_app(const std::string &projectName)
   {
     std::string readme;
-    readme.reserve(3000);
+    readme.reserve(3500);
 
     readme += "# " + projectName + "\n\n";
     readme += "Minimal Vix.cpp application.\n\n";
+
+    readme += "## Build & Run\n\n";
     readme += "```bash\n";
     readme += "vix build\n";
     readme += "vix run\n";
+    readme += "```\n\n";
+
+    readme += "## Configuration\n\n";
+    readme += "Vix applications **do not auto-load project configuration by default**.\n";
+    readme += "If you want to use a project-level configuration (for example to configure the server port),\n";
+    readme += "you must explicitly initialize and read it in your application.\n\n";
+
+    readme += "### Project config file\n\n";
+    readme += "Create a configuration file at:\n\n";
     readme += "```\n";
+    readme += "config/config.json\n";
+    readme += "```\n\n";
+
+    readme += "Example:\n\n";
+    readme += "```json\n";
+    readme += "{\n";
+    readme += "  \"server\": {\n";
+    readme += "    \"port\": 8081\n";
+    readme += "  }\n";
+    readme += "}\n";
+    readme += "```\n\n";
+
+    readme += "### Using the config in code\n\n";
+    readme += "To use the project configuration, initialize and read it explicitly:\n\n";
+    readme += "```cpp\n";
+    readme += "#include <vix.hpp>\n";
+    readme += "using namespace vix;\n\n";
+    readme += "int main()\n";
+    readme += "{\n";
+    readme += "  // Load project config (project config overrides Vix install config)\n";
+    readme += "  auto &cfg = vix::config::Config::getInstance();\n\n";
+    readme += "  App app;\n";
+    readme += "  app.get(\"/\", [](Request&, Response& res) {\n";
+    readme += "    res.send(\"Hello world\");\n";
+    readme += "  });\n\n";
+    readme += "  app.run(cfg.getServerPort());\n";
+    readme += "}\n";
+    readme += "```\n\n";
+
+    readme += "> The project `config/config.json` always takes precedence over the global Vix installation config.\n";
 
     return readme;
   }