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/dialog/export/codec/av1section.h

@@ -19,8 +19,8 @@
 
 ***/
 
-#ifndef AV1SECTION_H
-#define AV1SECTION_H
+#ifndef OAK_AV1SECTION_H
+#define OAK_AV1SECTION_H
 
 #include <QSlider>
 #include <QStackedWidget>
@@ -37,13 +37,13 @@ class AV1CRFSection : public QWidget {
 public:
 	AV1CRFSection(int default_crf, QWidget *parent = nullptr);
 
-	int GetValue() const;
+	int get_value() const;
 
-	static const int kDefaultAV1CRF = 30;
+	static const int k_default_a_v1_crf = 30;
 
 private:
-	static const int kMinimumCRF = 0;
-	static const int kMaximumCRF = 63;
+	static const int k_minimum_crf = 0;
+	static const int k_maximum_crf = 63;
 
 	QSlider *crf_slider_;
 };
@@ -52,13 +52,13 @@ class AV1Section : public CodecSection {
 	Q_OBJECT
 public:
 	enum CompressionMethod {
-		kConstantRateFactor,
+		k_constant_rate_factor,
 	};
 
 	AV1Section(QWidget *parent = nullptr);
 	AV1Section(int default_crf, QWidget *parent);
 
-	virtual void AddOpts(EncodingParams *params) override;
+	virtual void add_opts(EncodingParams *params) override;
 
 private:
 	QStackedWidget *compression_method_stack_;
@@ -70,4 +70,4 @@ private:
 
 }
 
-#endif // AV1SECTION_H
+#endif // OAK_AV1SECTION_H