Remove expired Sevalla, KaasHosting and Quantumweb sponsorships

[simonhamp]

Summary

• Sevalla, KaasHosting and Quantumweb sponsorships have ended, so their logos and links are removed from the home page Partners section.
• Deletes the now-unused logo Blade components (sponsors.logos.{sevalla,kaashosting,quantumweb}), the orphaned sponsors/lists/{docs,home}/corporate-sponsors.blade.php lists (no longer referenced anywhere), and the standalone public/img/sponsors/kaashosting.svg asset.
• The empty sponsor-logos grid wrapper inside components/home/partners.blade.php is also removed since no sponsor cards remain in it.

Test plan

• Visit the homepage and confirm the Partners section renders only the featured partners (Nexcalia, Web Mavens, Synergi Tech, Laradevs, BeyondCode) plus the Join CTA, with no leftover empty grid or expired sponsor cards.
• Verify no Blade compilation errors elsewhere on the site (docs sidebar, blog sidebar, article pages) — the deleted corporate-sponsors files were not referenced, but a quick smoke test of those pages confirms it.

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