Clean HTML headings to align with SEO best practices

[fthobe]

Summary

After long discussions in #377 it was agreed to implement changes in accordance with Issue #375 to clean HTML Headings for SEO in preparation of structured data update.

The contained commit practically does the following:

• where appropriate it removes html heading tags from html to allow a concentration of admin panel controlled SEO elements (Taxon Name / Product Name)
• elements relevant only for structured data such as prices, product names in taxon pages,.... have been entirely stripped of H tags in favour in page resource controls
• where it was possible H tags have simply been substituted with span, where not more complex html invoking tailwind classes has been added
• to avoid visual change even if a H tag was converted to span, the tailwind class text-hX has been kept

Checklist

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