Fixes for product feed, coupons, report export and API filter

For products with variants, the product code contains a slash or a space (e.g. 12345/ABC). Different feeds stored the same product with a slash in one and an underscore in another, so the code from the order did not match the product in the feed. As a result, automated emails (last purchased products) showed the price and name, but the description, product link and image were missing. Product codes are now normalised before comparison, so the product is found in the feed regardless of whether it's stored with a slash, a space, or an underscore.

Coupons with an expired validity date were imported into the account via the Eshop‑rychle and Upgates integrations even after expiring, which then got deleted and re‑imported day after day. Only coupons valid today or in the future are now imported; a coupon without a validity date is treated as permanently valid. The change only affects future synchronisations and does not touch coupons already in accounts.

When using the "All in list" option, the export ignored the applied filters (date range, type, name) and exported the entire campaign list. The export now matches what the user actually sees after filtering. If a user selects all records and then manually deselects some, the export only includes the records that remain selected.

The campaign log endpoint always returned an empty result when filtering by the not_opened event, even for campaigns with demonstrably unopened emails. The filter now returns the correct list of contacts who did not open the campaign.