style: unify identifier naming per updated conventions

Automated with clang-tidy readability-identifier-naming (config added to
.clang-tidy) plus scripted passes, per the updated rules now documented
in CONTRIBUTING.md:

- types (class/struct/enum/alias/template params): PascalCase
- functions, variables, members: snake_case (incl. rational -> Rational)
- private/protected members: trailing underscore; static member
  variables likewise (instance_, available_themes_)
- constants and enum values: snake_case (kLinear -> k_linear,
  F32P -> f32p); ALL_CAPS reserved for macros
- macros: OAK_ prefix (OLIVE_ADD_TEST/OLIVE_ASSERT/OLIVE_CONFIG ->
  OAK_ADD_TEST/OAK_ASSERT/OAK_CONFIG, GL_PREAMBLE -> OAK_GL_PREAMBLE,
  include guards -> OAK_*)
- file names: all lowercase (Current/Plugin/OliveHost/OliveClip/
  OlivePluginInstance -> current/plugin/olivehost/oliveclip/
  oliveplugininstance)
- getters share the member name sans underscore, setters set_foo()
- Qt and third-party (OpenFX) virtual overrides and framework callbacks
  keep their original names (exempt in .clang-tidy)

Manual follow-ups required where automation could not reach:
- string-based QMetaObject/SIGNAL/SLOT references updated to renamed
  methods (AddTask, CreatedFile, DeleteSpecificFile, moveSelectionUp, ...)
- macro bodies referencing renamed methods (OLIVE_CONFIG,
  NODE_DEFAULT_DESTRUCTOR, MANAGEDDISPLAYWIDGET_*)
- self-shadowing locals renamed where signals/methods became same-named
  (size_changed, worker_count, selected_items, import param, filters)
- third_party OFX member/namespace usages restored (OFX::Host::*,
  _created, _clipPrefsDirty, createInstance, clearPersistentMessage)
- STL protocol aliases restored (const_iterator) with .clang-tidy
  ignore rules; qHash overloads restored

Full build and test suite pass: ctest 4/4, ~1960 gtest cases green.

app/config/config.h

@@ -19,8 +19,8 @@
 
 ***/
 
-#ifndef CONFIG_H
-#define CONFIG_H
+#ifndef OAK_CONFIG_H
+#define OAK_CONFIG_H
 
 #include <QMap>
 #include <QString>
@@ -31,24 +31,24 @@
 namespace olive
 {
 
-#define OLIVE_CONFIG(x) Config::Current()[QStringLiteral(x)]
-#define OLIVE_CONFIG_STR(x) Config::Current()[x]
+#define OAK_CONFIG(x) Config::current()[QStringLiteral(x)]
+#define OAK_CONFIG_STR(x) Config::current()[x]
 
 class Config {
 public:
-	static Config &Current();
+	static Config &current();
 
-	void SetDefaults();
+	void set_defaults();
 
-	static void Load();
+	static void load();
 
-	static void Save();
+	static void save();
 
 	QVariant operator[](const QString &) const;
 
 	QVariant &operator[](const QString &);
 
-	NodeValue::Type GetConfigEntryType(const QString &key) const;
+	NodeValue::Type get_config_entry_type(const QString &key) const;
 
 private:
 	Config();
@@ -58,16 +58,16 @@ private:
 		QVariant data;
 	};
 
-	void SetEntryInternal(const QString &key, NodeValue::Type type,
+	void set_entry_internal(const QString &key, NodeValue::Type type,
 						  const QVariant &data);
 
 	QMap<QString, ConfigEntry> config_map_;
 
-	static Config current_config_;
+	static Config current_config;
 
-	static QString GetConfigFilePath();
+	static QString get_config_file_path();
 };
 
 }
 
-#endif // CONFIG_H
+#endif // OAK_CONFIG_H