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/timeline/timelinecommon.h

@@ -19,8 +19,8 @@
 
 ***/
 
-#ifndef TIMELINECOMMON_H
-#define TIMELINECOMMON_H
+#ifndef OAK_TIMELINECOMMON_H
+#define OAK_TIMELINECOMMON_H
 
 #include <olive/core/core.h>
 
@@ -36,20 +36,20 @@ class Track;
 
 class Timeline {
 public:
-	enum MovementMode { kNone, kMove, kTrimIn, kTrimOut };
+	enum MovementMode { k_none, k_move, k_trim_in, k_trim_out };
 
-	enum ThumbnailMode { kThumbnailOff, kThumbnailInOut, kThumbnailOn };
+	enum ThumbnailMode { k_thumbnail_off, k_thumbnail_in_out, k_thumbnail_on };
 
-	enum WaveformMode { kWaveformsDisabled, kWaveformsEnabled };
+	enum WaveformMode { k_waveforms_disabled, k_waveforms_enabled };
 
-	static bool IsATrimMode(MovementMode mode)
+	static bool is_a_trim_mode(MovementMode mode)
 	{
-		return mode == kTrimIn || mode == kTrimOut;
+		return mode == k_trim_in || mode == k_trim_out;
 	}
 
 	struct EditToInfo {
 		Track *track;
-		rational nearest_time;
+		Rational nearest_time;
 		Block *nearest_block;
 	};
 };
@@ -58,4 +58,4 @@ public:
 
 }
 
-#endif // TIMELINECOMMON_H
+#endif // OAK_TIMELINECOMMON_H