add RPC fallback

[timbrinded]

No description provided.

[Copilot]

Pull request overview

Adds multi-RPC fallback support to the frontend’s wagmi/RainbowKit configuration so the app can fail over between multiple RPC endpoints per chain.

Changes:

• Introduces per-chain RPC URL lists (optionally preferring env-provided URLs) and builds a fallback(...) transport with per-URL HTTP timeouts.
• Updates wagmi transports to use the new fallback transport for Sepolia, Base Sepolia, and Arbitrum Sepolia.
• Extends fe/.env.example with WalletConnect project id and optional RPC override variables.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
fe/app/config/wagmi.ts	Builds RPC URL lists and switches wagmi transports to a fallback transport with timeouts.
fe/.env.example	Documents optional RPC override env vars and adds WalletConnect project id example.

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[Copilot]

splitRpcUrls will throw when the env var is undefined. value?.split(",") returns undefined when value is missing, but .map(...) then runs on that undefined. Use optional chaining for the whole chain (e.g. value?.split(",")?.map(... )?.filter(...) ?? []) or parenthesize the split result before mapping.

Suggested change

	.map((url) => url.trim())
	.filter(Boolean) ?? [];
	?.map((url) => url.trim())
	?.filter(Boolean) ?? [];

[Copilot]

In .env.example, setting VITE_WALLETCONNECT_PROJECT_ID=replace-me will override the in-code fallback ("demo") and likely break WalletConnect for anyone who copies this file verbatim. Consider leaving it blank/commented out or setting it to demo with a note that a real project id is required for production.

Suggested change

	VITE_WALLETCONNECT_PROJECT_ID=replace-me
	# WalletConnect project id. "demo" is suitable for local development only;
	# replace this with a real project id for production.
	VITE_WALLETCONNECT_PROJECT_ID=demo