Implemented shared S3 audio caching for prepare and restore --include-audio

internal/config/config.go

@@ -19,6 +19,7 @@ type PipelineConfig struct {
 	Workspace    WorkspaceConfig    `yaml:"workspace"`
 	Storage      StorageConfig      `yaml:"storage"`
 	Spool        SpoolConfig        `yaml:"spool"`
+	Cache        CacheConfig        `yaml:"cache"`
 	Archive      *ArchiveConfig     `yaml:"archive"`
 	Secrets      *SecretsConfig     `yaml:"secrets"`
 	WhisperX     WhisperXConfig     `yaml:"whisperx"`
@@ -90,6 +91,12 @@ type SpoolConfig struct {
 	DeleteAudioAfterArchive bool   `yaml:"delete_audio_after_archive"`
 }
 
+// CacheConfig configures durable local caches for reusable remote inputs.
+type CacheConfig struct {
+	Root    string `yaml:"root"`
+	S3Audio *bool  `yaml:"s3_audio"`
+}
+
 // ArchiveConfig configures archive behavior and artifact promotions.
 type ArchiveConfig struct {
 	Enabled          *bool                  `yaml:"enabled"`