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/audio/audiowaveformsync.h

@@ -18,8 +18,8 @@
 
 ***/
 
-#ifndef AUDIOWAVEFORMSYNC_H
-#define AUDIOWAVEFORMSYNC_H
+#ifndef OAK_AUDIOWAVEFORMSYNC_H
+#define OAK_AUDIOWAVEFORMSYNC_H
 
 #include <cstdint>
 
@@ -48,15 +48,15 @@ public:
 		bool valid = false;
 	};
 
-	static QVector<double> ExtractRmsEnvelope(const core::SampleBuffer &samples,
+	static QVector<double> extract_rms_envelope(const core::SampleBuffer &samples,
 											  size_t window_samples);
 
-	static OffsetResult EstimateOffset(const core::SampleBuffer &reference,
+	static OffsetResult estimate_offset(const core::SampleBuffer &reference,
 									   const core::SampleBuffer &candidate,
 									   size_t window_samples,
 									   int64_t max_offset_samples);
 
-	static OffsetResult EstimateEnvelopeOffset(const QVector<double> &reference,
+	static OffsetResult estimate_envelope_offset(const QVector<double> &reference,
 											   const QVector<double> &candidate,
 											   size_t window_samples,
 											   int64_t max_offset_windows);
@@ -71,7 +71,7 @@ public:
 	 * waveform cache have not been generated yet. Empty masks are treated as
 	 * "all windows valid".
 	 */
-	static OffsetResult EstimateEnvelopeOffset(const QVector<double> &reference,
+	static OffsetResult estimate_envelope_offset(const QVector<double> &reference,
 											   const QVector<double> &candidate,
 											   const QVector<bool> &reference_valid,
 											   const QVector<bool> &candidate_valid,
@@ -89,7 +89,7 @@ public:
 	 * callers should bound max_offset_windows to a sensible range.
 	 */
 	static StretchOffsetResult
-	EstimateStretchAndOffset(const QVector<double> &reference,
+	estimate_stretch_and_offset(const QVector<double> &reference,
 							 const QVector<double> &candidate,
 							 const QVector<bool> &reference_valid,
 							 const QVector<bool> &candidate_valid, size_t window_samples,
@@ -99,4 +99,4 @@ public:
 
 }
 
-#endif // AUDIOWAVEFORMSYNC_H
+#endif // OAK_AUDIOWAVEFORMSYNC_H