bug: localStorage writes unsanitised for BigInt/circular values

[nanaf6203-bit]

Summary

Many localStorage writes stringify non-string values without verifying types, causing JSON.stringify to throw on circular refs or BigInts.

Affected area

• src/lib/cacheManager.ts (queue, cache config)
• src/lib/propertyCache.ts (propchain-search-cache)
• src/store/portfolioStore.ts
• src/components/dashboard/DraggablePropertiesList.tsx

Steps to reproduce / impact

If a BigInt sneaks into the saved value, JSON.stringify throws and the cache silently fails to persist. In DraggablePropertiesList, an unsorted ordering can persist via the failure path.

Expected behaviour

Wrap writers in a typed helper that sanitises values (BigInt → string, Reviver/Replacer pair) and uses the existing structured logger on failure.

Acceptance criteria

• Centralise localStorage writes in a small typed module.
• Add TypeScript types for each saved shape.
• Add unit tests for fail-safe paths.

[Killerjunior]

@Killerjunior has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hi maintainer, I have read and understood the issue requirements and checked the necessary documentation. I’m confident I can work on this task effectively and deliver a proper solution.

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[Priyanshu1-62]

@Priyanshu1-62 has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hi sir,
Please assign this issue to me, thanks.

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[DanielCharis1]

@DanielCharis1 has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

can i be assigned this

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This issue has been completed by @DanielCharis1 as part of the Stellar Wave Program's 6th Wave 🥳

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