extract shared TOML helpers into TomlHelpers.h/.cpp

ConfigLoader.cpp had grown to 877 lines by mixing generic TOML-parsing
helpers (used by every per-file loader) with per-domain parsing logic.
Splitting the file per config domain first requires pulling out the
helpers shared by two or more domains, so each domain .cpp can include
them without duplication. Pure move: no logic, message, or ordering
changes.

Co-Authored-By: Claude <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YHcUerKAZKWNvSKJxYKbnG

src/lib/config/TomlHelpers.h

@@ -0,0 +1,61 @@
+#pragma once
+
+#include <cstdint>
+#include <stdexcept>
+#include <string>
+#include <vector>
+
+#include "toml.hpp"
+
+#include "Formula.h"
+#include "RecipesConfig.h"  // for RecipeIngredient
+
+// Shared TOML-parsing helpers used by two or more ConfigLoader per-domain
+// loaders. Helpers used by exactly one domain stay local to that domain's
+// .cpp file instead.
+
+// --- Error helpers ----------------------------------------------------------
+
+std::runtime_error makeError(const std::string& file,
+                             const std::string& path,
+                             const std::string& why);
+
+// --- Typed accessors (throw on missing or wrong type) -----------------------
+
+int64_t requireInt(const toml::node_view<toml::node>& node,
+                   const std::string& file,
+                   const std::string& path);
+
+double requireDouble(const toml::node_view<toml::node>& node,
+                     const std::string& file,
+                     const std::string& path);
+
+std::string requireString(const toml::node_view<toml::node>& node,
+                          const std::string& file,
+                          const std::string& path);
+
+bool requireBool(const toml::node_view<toml::node>& node,
+                 const std::string& file,
+                 const std::string& path);
+
+const toml::array& requireArray(const toml::node_view<toml::node>& node,
+                                const std::string& file,
+                                const std::string& path);
+
+const toml::table& requireTable(const toml::node_view<toml::node>& node,
+                                const std::string& file,
+                                const std::string& path);
+
+Formula requireFormula(const toml::node_view<toml::node>& node,
+                       const std::string& file,
+                       const std::string& path);
+
+std::vector<std::string> requireStringArray(const toml::node_view<toml::node>& node,
+                                            const std::string& file,
+                                            const std::string& path);
+
+std::vector<RecipeIngredient> parseIngredients(const toml::array& arr,
+                                               const std::string& file,
+                                               const std::string& path);
+
+toml::table parseFile(const std::string& path, const std::string& file);