Public Access
The [data-bc-seats] line lived in the Price-and-booking section; the user wants it
just under the hero. Moved (not copied) on EN/DE/ES — one element per page, the same
/static/bootcamp-availability.js, every string unchanged ("x of 6 seats available" /
"x von 6 Plätzen frei" / "x de 6 plazas disponibles").
Also adds a page-scoped :disabled style for the Buy buttons so a sold-out cohort's
disabled buttons actually read as disabled (rule: zero is honest — the buy must not
look open). Buy forms untouched: still post product_id 17.