proxy: per-footage presets, audio in proxies, configurable ffmpeg path

- Footage can store custom proxy parameters (width/height/crf/preset/
  extension/audio) that override the global settings; they are
  serialized with the project and used by every generation entry point
  via Footage::GetEffectiveProxyParams()
- Proxies now include the source audio streams (AAC) unless disabled;
  the proxy filename records the audio flag and offline audio rendering
  decodes from the proxy when present
- ProxyTask resolves ffmpeg from the new FFmpegPath config key first,
  then PATH, then common install locations (e.g. Homebrew on macOS),
  instead of relying on PATH only; the error message points at the
  preferences when no executable is found
- ProxyTask::BuildArguments() is extracted for testability
- Add ProxyIncludeAudio and FFmpegPath config defaults
- Add regression tests for the filename audio marker, config-backed
  params, ffmpeg resolution, argument building, and custom-param
  persistence

app/codec/proxymanager.cpp

@@ -18,11 +18,14 @@
 
 #include "proxymanager.h"
 
+#include <QCoreApplication>
 #include <QDir>
 #include <QFileInfo>
 #include <QMutexLocker>
+#include <QStandardPaths>
 
 #include "common/filefunctions.h"
+#include "config/config.h"
 #include "task/proxy/proxy.h"
 #include "task/taskmanager.h"
 
@@ -36,7 +39,8 @@ bool ProxyParamsEqual(const ProxyManager::ProxyParams &a,
 {
 	return a.width == b.width && a.height == b.height &&
 		   a.version == b.version && a.extension == b.extension &&
-		   a.crf == b.crf && a.preset == b.preset;
+		   a.crf == b.crf && a.preset == b.preset &&
+		   a.include_audio == b.include_audio;
 }
 
 QString ProxyManager::GetProxyDirectory(const QString &cache_path)
@@ -53,11 +57,12 @@ QString ProxyManager::GetProxyFilename(const QString &cache_path,
 	const QString extension =
 		params.extension.isEmpty() ? QStringLiteral("mp4") : params.extension;
 	const QString filename =
-		QStringLiteral("%1-%2.%3x%4.v%5.%6")
+		QStringLiteral("%1-%2.%3x%4.v%5.a%6.%7")
 			.arg(FileFunctions::GetUniqueFileIdentifier(source_filename),
 				 QString::number(stream_index), QString::number(params.width),
-				 QString::number(params.height),
-				 QString::number(params.version), extension);
+				 QString::number(params.height), QString::number(params.version),
+				 params.include_audio ? QStringLiteral("1") : QStringLiteral("0"),
+				 extension);
 
 	return QDir(proxy_dir).filePath(filename);
 }
@@ -117,6 +122,70 @@ ProxyManager::ProxyStateFromString(const QString &state)
 	return kProxyMissing;
 }
 
+bool ProxyManager::ProxyFilenameHasAudio(const QString &proxy_filename)
+{
+	return QFileInfo(proxy_filename).fileName().contains(
+		QStringLiteral(".a1."));
+}
+
+ProxyManager::ProxyParams ProxyManager::ProxyParamsFromConfig()
+{
+	ProxyParams params;
+	params.width = OLIVE_CONFIG("ProxyWidth").value<int>();
+	params.height = OLIVE_CONFIG("ProxyHeight").value<int>();
+	params.crf = OLIVE_CONFIG("ProxyCRF").value<int>();
+	params.preset = OLIVE_CONFIG("ProxyPreset").toString();
+	params.include_audio = OLIVE_CONFIG("ProxyIncludeAudio").toBool();
+	return params;
+}
+
+QString ProxyManager::FindFFmpegExecutable(const QString &configured_path)
+{
+	// An explicitly configured path takes precedence if it is usable
+	if (!configured_path.isEmpty()) {
+		const QFileInfo configured_info(configured_path);
+		if (configured_info.exists() && configured_info.isFile() &&
+			configured_info.isExecutable()) {
+			return configured_info.absoluteFilePath();
+		}
+
+		qWarning() << "Configured ffmpeg path is not a valid executable:"
+				   << configured_path;
+	}
+
+	// Fall back to searching the system PATH
+	const QString from_path =
+		QStandardPaths::findExecutable(QStringLiteral("ffmpeg"));
+	if (!from_path.isEmpty()) {
+		return from_path;
+	}
+
+	// Finally, try common install locations (PATH on GUI-launched apps,
+	// particularly on macOS, often lacks these)
+	QStringList candidates;
+	candidates.append(QCoreApplication::applicationDirPath() +
+					  QStringLiteral("/ffmpeg"));
+#ifdef Q_OS_MAC
+	candidates.append(QStringLiteral("/opt/homebrew/bin/ffmpeg"));
+	candidates.append(QStringLiteral("/usr/local/bin/ffmpeg"));
+#endif
+#ifdef Q_OS_WINDOWS
+	candidates.append(QCoreApplication::applicationDirPath() +
+					  QStringLiteral("/ffmpeg.exe"));
+#endif
+	candidates.append(QStringLiteral("/usr/bin/ffmpeg"));
+	candidates.append(QStringLiteral("/usr/local/bin/ffmpeg"));
+
+	for (const QString &candidate : candidates) {
+		const QFileInfo info(candidate);
+		if (info.exists() && info.isFile() && info.isExecutable()) {
+			return info.absoluteFilePath();
+		}
+	}
+
+	return QString();
+}
+
 ProxyManager::Proxy
 ProxyManager::GetOrStartProxy(const QString &cache_path,
 							  const QString &source_filename, int stream_index,