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/codec/timecodemetadata.cpp

@@ -29,8 +29,8 @@ namespace olive
 {
 
 TimecodeMetadata::SourceTime
-TimecodeMetadata::FromTimecodeString(const QString &timecode,
-									 const core::rational &timebase)
+TimecodeMetadata::from_timecode_string(const QString &timecode,
+									 const core::Rational &timebase)
 {
 	SourceTime result;
 	const QString trimmed = timecode.trimmed();
@@ -40,8 +40,8 @@ TimecodeMetadata::FromTimecodeString(const QString &timecode,
 
 	bool ok = false;
 	const core::Timecode::Display display =
-		trimmed.contains(';') ? core::Timecode::kTimecodeDropFrame :
-								core::Timecode::kTimecodeNonDropFrame;
+		trimmed.contains(';') ? core::Timecode::k_timecode_drop_frame :
+								core::Timecode::k_timecode_non_drop_frame;
 	result.time = core::Timecode::timecode_to_time(trimmed.toStdString(),
 												   timebase, display, &ok);
 	result.valid = ok;
@@ -52,7 +52,7 @@ TimecodeMetadata::FromTimecodeString(const QString &timecode,
 }
 
 TimecodeMetadata::SourceTime
-TimecodeMetadata::FromBwfTimeReference(const QString &time_reference,
+TimecodeMetadata::from_bwf_time_reference(const QString &time_reference,
 									   int sample_rate)
 {
 	SourceTime result;
@@ -75,10 +75,10 @@ TimecodeMetadata::FromBwfTimeReference(const QString &time_reference,
 	const qulonglong rational_limit =
 		static_cast<qulonglong>(std::numeric_limits<int>::max());
 	if (numerator <= rational_limit && denominator <= rational_limit) {
-		result.time = core::rational(static_cast<int>(numerator),
+		result.time = core::Rational(static_cast<int>(numerator),
 									 static_cast<int>(denominator));
 	} else {
-		result.time = core::rational::fromDouble(
+		result.time = core::Rational::from_double(
 			static_cast<double>(samples) / static_cast<double>(sample_rate));
 	}
 	result.source = QStringLiteral("bwf_time_reference");