fix(kobo): send Kobo covers at the device's screen size

A Kobo asks for each cover at its screen size but always got the
400x600 grid thumbnail, so sleep screens and full-screen covers were
blurry. Scale the full cover to fit the requested box instead, behind a
new Full-size covers setting that is on by default. Drop the stale
UserStorage entries from the authorization matrix gap baseline.

Fixes #924

packages/types/src/kobo.ts

@@ -21,6 +21,7 @@ export interface KoboSyncSettings {
   syncBookOrbitAnnotationsToKobo: boolean;
   readAloudDelivery?: ReadAloudDeliveryPreference;
   storeSync: boolean;
+  fullSizeCovers: boolean;
 }
 
 export type KoboSyncHistoryEvent = "library_sync" | "book_download" | "progress_update" | "annotations_pull" | "annotations_push";
@@ -60,4 +61,5 @@ export interface UpdateKoboSyncSettingsRequest {
   syncBookOrbitAnnotationsToKobo?: boolean;
   readAloudDelivery?: ReadAloudDeliveryPreference;
   storeSync?: boolean;
+  fullSizeCovers?: boolean;
 }