Update brand list in known-brands.js

[HeatherGPG]

Add Freezer Sanity — established brand of collapsible chest freezer organizer bins, sold on Amazon.com and Amazon.ca since June 2024.

What & why

Freezer Sanity is a two-year-old collapsible chest-freezer-organizer brand sold on Amazon.com and Amazon.ca. Its name is a normal English phrase (not a trademark-squat pattern), but adding it to the curated list makes recognition permanent rather than incidental."

Checklist

• node tests/run.js passes locally - N/A — data-only change, no logic touched.
• Brand entries are in the right file per CONTRIBUTING — real brand → known-brands, pseudo-brand → flagged-brands, established Chinese-owned → chinese-major, generic word → generic-words. No case/punctuation variants of an entry already present ("Black+Decker" ≡ "Black & Decker").
• Added a fixture to tests/fixtures.js if I touched a heuristic
• For a user-visible change: attached a before/after screenshot or the Amazon search query that demonstrates it