Bound the remaining local withTimeout copies to lib/with-timeout.ts

[Jaydbrown]

The shared withTimeout exists but stale branches keep reintroducing local copies (create page, WalletContext). Add a no-restricted-syntax lint against a local function withTimeout.

[malaysiaonelove]

Hi maintainer, I’m interested in working on this issue. I have relevant experience and have reviewed the requirements. Please assign it to me I’m confident I can deliver a high-quality solution.

[ZacLou]

I'd like to work on this issue. I have relevant experience with this tech stack and can deliver a clean, well-tested PR. I can submit within 1-2 days.

[ZacLou]

Submitted PR #503 adding the lint rule. Tested that both function declarations and arrow-function assignments are caught, while lib/with-timeout.ts remains exempt.