refactor: remove thumbnail preview feature

internal/features/playback/service.go

@@ -14,7 +14,6 @@ import (
 	"sort"
 	"strconv"
 	"strings"
-	"sync"
 	"time"
 
 	"mal/internal/jikan"
@@ -25,11 +24,6 @@ type Service struct {
 	jikanClient    *jikan.Client
 	httpClient     *http.Client
 	db             database.Querier
-	previewRoot    string
-	previewMu      sync.Mutex
-	previewLocks   map[string]*sync.Mutex
-	previewFailMu  sync.Mutex
-	previewFailTTL map[string]time.Time
 }
 
 type sourceScore struct {
@@ -47,9 +41,6 @@ func NewService(jikanClient *jikan.Client, db database.Querier) *Service {
 		jikanClient:    jikanClient,
 		httpClient:     &http.Client{Timeout: 12 * time.Second},
 		db:             db,
-		previewRoot:    newPreviewRootDir(),
-		previewLocks:   make(map[string]*sync.Mutex),
-		previewFailTTL: make(map[string]time.Time),
 	}
 }