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/widget/timelinewidget/timelinewidgetwaveformsync.h

@@ -19,8 +19,8 @@
 
 ***/
 
-#ifndef TIMELINEWIDGETWAVEFORMSYNC_H
-#define TIMELINEWIDGETWAVEFORMSYNC_H
+#ifndef OAK_TIMELINEWIDGETWAVEFORMSYNC_H
+#define OAK_TIMELINEWIDGETWAVEFORMSYNC_H
 
 #include <QVector>
 
@@ -49,7 +49,7 @@ struct WaveformSyncClip {
  *
  * Kept in a separate unit so they can be exercised directly by unit tests.
  */
-namespace TimelineWaveformSync
+namespace timeline_waveform_sync
 {
 
 /**
@@ -59,13 +59,13 @@ namespace TimelineWaveformSync
  * has been validated in the waveform cache. Previously the whole range had to
  * be validated, which made the context-menu action unavailable for long clips.
  */
-bool GetWaveformSyncClip(Block *block, WaveformSyncClip *out);
+bool get_waveform_sync_clip(Block *block, WaveformSyncClip *out);
 
 /**
  * @brief Return all selected blocks that can be synchronized by waveform.
  */
 QVector<WaveformSyncClip>
-GetSelectedWaveformSyncClips(const QVector<Block *> &blocks);
+get_selected_waveform_sync_clips(const QVector<Block *> &blocks);
 
 /**
  * @brief Extract a peak envelope from the validated regions of a waveform cache.
@@ -76,7 +76,7 @@ GetSelectedWaveformSyncClips(const QVector<Block *> &blocks);
  * actually cached, allowing the correlation to skip uncached regions instead
  * of treating them as silence.
  */
-QVector<double> ExtractWaveformCacheEnvelope(const WaveformSyncClip &clip,
+QVector<double> extract_waveform_cache_envelope(const WaveformSyncClip &clip,
 											 int sample_rate,
 											 size_t window_samples,
 											 QVector<bool> *valid_mask = nullptr);
@@ -85,4 +85,4 @@ QVector<double> ExtractWaveformCacheEnvelope(const WaveformSyncClip &clip,
 
 } // namespace olive
 
-#endif // TIMELINEWIDGETWAVEFORMSYNC_H
+#endif // OAK_TIMELINEWIDGETWAVEFORMSYNC_H