Final cleanup: Update remaining comments and variable names

Changes:
- Update comments: "Bookmann UUID" → "Bookhoard UUID"
- Rename sidecar struct field: Bookmann → Bookhoard
- Update type names: SidecarBookmannConfig → SidecarBookhoardConfig
- Fix test database name in queue_test.go
- Fix uppercase env var examples in KOBO_SETUP.md

Internal Go variable names (BookmannUuid, bookmannUUID) left unchanged
as they're implementation details that don't affect functionality.

Part of project rename to Bookhoard.

internal/database/querier.go

@@ -130,7 +130,7 @@ type Querier interface {
 	GetDevice(ctx context.Context, id pgtype.UUID) (Devices, error)
 	GetDeviceByAuthToken(ctx context.Context, authToken string) (Devices, error)
 	GetDeviceByIdentifier(ctx context.Context, deviceIdentifier string) (Devices, error)
-	// Get device catalog by Bookmann UUID
+	// Get device catalog by Bookhoard UUID
 	GetDeviceCatalogByBookhoardUUID(ctx context.Context, arg GetDeviceCatalogByBookhoardUUIDParams) (DeviceCatalogs, error)
 	// Get device catalog by Kobo ContentId
 	GetDeviceCatalogByKoboContentId(ctx context.Context, koboContentID string) (DeviceCatalogs, error)

internal/database/queries.sql.go

@@ -1828,7 +1828,7 @@ type GetDeviceCatalogByBookhoardUUIDParams struct {
 	BookmannUuid pgtype.UUID `db:"bookhoard_uuid" json:"bookhoard_uuid"`
 }
 
-// Get device catalog by Bookmann UUID
+// Get device catalog by Bookhoard UUID
 func (q *Queries) GetDeviceCatalogByBookhoardUUID(ctx context.Context, arg GetDeviceCatalogByBookhoardUUIDParams) (DeviceCatalogs, error) {
 	row := q.db.QueryRow(ctx, GetDeviceCatalogByBookhoardUUID, arg.DeviceID, arg.BookmannUuid)
 	var i DeviceCatalogs