[feature] Product/Restock alerts - should have also `PreStock` mode

Would be really nice to have more modes detected for changes with the restock monitor

`In Stock` , `Out of Stock`, and in this case `PreSale`

There is also the "text" `In Kürze lieferbar` to be added to a different list of JS texts

So for example


and we have

```

{
"@context": "https://schema.org/",
"@type": "Product",
"name": "ASUS ROG Astral GeForce RTX 5090 OC 32GB",
"image": "https://website.de/422x390/products/2149471",
"url": "https://website.de/produkt/959842/asus-rog-astral-geforce-rtx-5090-oc-32gb.html",
"brand": {
"@type": "Brand",
"name": "ASUS"
},
"description": "Hinweis: Verwende nur die mitgelieferten Kabel",
"sku": "959842",
"offers": {
"@type": "Offer",
"priceCurrency": "EUR",
"price": "2998",
"availability": "https://schema.org/PreSale",
"itemCondition": "https://schema.org/NewCondition"
}}

```

Start by locating the restock monitor's availability-mode detection and the JavaScript text lists. Trace how schema.org `PreSale` and the text `In Kürze lieferbar` are classified, then confirm the intended distinction between the issue's `PreStock` and `PreSale` names. Done means both availability signals are detected as the appropriate restock mode.

Written by the indexing model from the issue text.