fix: fallback to chainId of wallet

[iamacook]

What it solves

Resolves #1554

How this PR fixes it

useChainId returns the chainId of the connected wallet if no chainId is present in the URL or cached from the last session.

How to test it

1. Open a "non-chainId" URL in an Incognito window (e.g. /welcome).
2. Ensure the wallet is connected to a chain that is present in the environment chain configuration and connect the wallet.
3. Observe the chain in the top right matches that of the wallet.

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1. Open a "non-chainId" URL in an Incognito window (e.g. /welcome).
2. Ensure the wallet is connected to a chain that is NOT present in the environment chain configuration and connect the wallet.
3. Observe the chain in the top right is the default fallback, Mainnet on prod. or Goerli on dev.

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Branch preview

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https://fallback_wallet_chainid--webcore.review-web-core.5afe.dev

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Type	Occurrences	Fixable
Errors	0	0
Warnings	0	0
Ignored	0	N/A

• Result: ✅ success
• Annotations: 0 total

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^{Report generated by eslint-plus-action}

[katspaugh]

I would define the wallet chainId as a separate thing and fall back in this order:

  return urlChainId || walletChainId || session.lastChainId || fallbackChainId

[usame-algan]

Is fallbackChainId and walletChainId the same thing?

[iamacook]

I've inverted the order and added tests to cover it.

[iamacook]

Is fallbackChainId and walletChainId the same thing?

In my previous commit, fallbackChainId was either that of the wallet or from defaultChainId. I've changed it in accordance with the first suggestion. Wdyt?

[katspaugh]

Thanks! 👍

[katspaugh]

Tested, it correctly sets the app network with the current wallet network if you're on a page w/o a Safe address or ?chain= in the URL. ✅
It even changes the app network when you change the wallet network.
It briefly flashes the initial default network on page load, but that's expected.

On pages with a Safe address or the chain query param, it works the same as before.