feat: migrate playback module to modular domain pattern

internal/domain/provider.go

@@ -0,0 +1,27 @@
+package domain
+
+import (
+	"context"
+)
+
+type StreamSource struct {
+	URL     string
+	Quality string
+}
+
+type StreamResult struct {
+	URL        string
+	Referer    string
+	Subtitles  []Subtitle
+	Qualities  []StreamSource
+}
+
+type Subtitle struct {
+	URL   string
+	Label string
+}
+
+type Provider interface {
+	Name() string
+	GetStreams(ctx context.Context, animeID int, episode string, mode string) (*StreamResult, error)
+}