feat(backend): directory scanner — diff, error state, covers, cache sweep, redis lock

backend/internal/api/api.go

@@ -9,6 +9,7 @@ import (
 	"booklib/internal/auth"
 	"booklib/internal/config"
 	"booklib/internal/redispkg"
+	"booklib/internal/scanner"
 	"booklib/internal/store"
 )
 
@@ -16,6 +17,7 @@ type api struct {
 	cfg *config.Config
 	st  *store.Store
 	rdb *redispkg.R
+	sc  *scanner.Scanner
 }
 
 func err(c *gin.Context, status int, code, msg string) {