Fix: Display Applied Sticker Slabs on Market Pages

[GODrums]

Fixes the parsing for Sticker Slabs in our custom sticker display on market pages:

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Note

• Keychain parsing: Updates loadKeychains to allow HTML descriptions containing Sticker Slab while still excluding regular sticker entries, enabling Sticker Slab rendering.
• Value handling: In renderAppliedItem, only renders the item-value span when item.value is present; and keychain value formatter now returns an empty string when no pattern exists (e.g., Sticker Slabs).

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