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/render/lutlibrary.h

@@ -18,8 +18,8 @@
 
 ***/
 
-#ifndef LUTLIBRARY_H
-#define LUTLIBRARY_H
+#ifndef OAK_LUTLIBRARY_H
+#define OAK_LUTLIBRARY_H
 
 #include <QString>
 #include <QStringList>
@@ -41,18 +41,18 @@ public:
 	 * @brief Returns true if the given file suffix is a supported LUT
 	 * extension (.cube or .3dl, case-insensitive, leading dot tolerated)
 	 */
-	static bool IsSupportedExtension(const QString &suffix);
+	static bool is_supported_extension(const QString &suffix);
 
 	/**
 	 * @brief The directories that make up the LUT library
 	 */
-	static QStringList GetDirectories();
+	static QStringList get_directories();
 
 	/**
 	 * @brief Replaces the LUT library directories and saves them to the
 	 * application config
 	 */
-	static void SetDirectories(const QStringList &dirs);
+	static void set_directories(const QStringList &dirs);
 
 	/**
 	 * @brief All supported LUT files found under the library directories
@@ -60,9 +60,9 @@ public:
 	 * Directories are scanned recursively. Files in earlier directories
 	 * are listed first.
 	 */
-	static QStringList GetLutFiles();
+	static QStringList get_lut_files();
 };
 
 }
 
-#endif // LUTLIBRARY_H
+#endif // OAK_LUTLIBRARY_H