feat: add Openfort Signer docs

[Huguet57]

Adds documentation for the Openfort signer integration with Safe SDK.

[Huguet57]

Related PR: 5afe/safe-signers#2

[Huguet57]

Hi team, just passing by to bring a new integration with Openfort. Keep up the good work! :)

[emauja]

Update to @openfort/react v1.0.4 API

The Openfort React SDK has been updated to v1.0.4 with breaking changes. Here are the required updates for this PR:

Changes needed in pages/sdk/signers/openfort.mdx:

1. Move getDefaultConfig import to the new @openfort/react/wagmi subpath
2. Replace useWallets with useEthereumEmbeddedWallet from @openfort/react/ethereum
3. Update documentation text to reference the new hook name

Diff

-  import { OpenfortProvider, OpenfortButton, useUser, useWallets, useOpenfort, AccountTypeEnum, AuthProvider, getDefaultConfig } from '@openfort/react'
+  import { OpenfortProvider, OpenfortButton, useUser, useOpenfort, AccountTypeEnum, AuthProvider } from '@openfort/react'
+  import { getDefaultConfig } from '@openfort/react/wagmi'
+  import { useEthereumEmbeddedWallet } from '@openfort/react/ethereum'

-  const { wallets } = useWallets()
+  const { wallets } = useEthereumEmbeddedWallet()

A branch with these changes applied is available at emauja:feat/openfort-signer.

These changes align with the v1.0.0 breaking changes where wagmi utilities moved to @openfort/react/wagmi and wallet hooks were split into chain-specific subpaths (@openfort/react/ethereum, @openfort/react/solana).

[emauja]

Openfort React SDK v1.0.4 Update Required

After researching the latest @openfort/react v1.0.4 API, several imports and hooks in this PR need updating:

1. getDefaultConfig moved to subpath import

Since v1.0.0, wagmi utilities are in a separate subpath:

- import { OpenfortProvider, OpenfortButton, useUser, useWallets, useOpenfort, AccountTypeEnum, AuthProvider, getDefaultConfig } from '@openfort/react'
+ import { OpenfortProvider, OpenfortButton, useUser, useOpenfort, AccountTypeEnum, AuthProvider } from '@openfort/react'
+ import { getDefaultConfig } from '@openfort/react/wagmi'
+ import { useEthereumEmbeddedWallet } from '@openfort/react/ethereum'

2. useWallets removed — use useEthereumEmbeddedWallet instead

useWallets() no longer exists in v1.0.4. Replace with:

- const { wallets } = useWallets()
+ const evm = useEthereumEmbeddedWallet()

3. Update wallet access pattern

- if (isAuthenticated && wallets.length > 0) {
+ if (isAuthenticated && evm.status === 'connected') {
    ...
-   const signer = wallets[0].address
+   const signer = evm.address
  }
- }, [isAuthenticated, wallets])
+ }, [isAuthenticated, evm.status])

4. Update description text

- hooks like `useUser()` or `useWallets()` that will provide
+ hooks like `useUser()` or `useEthereumEmbeddedWallet()` that will provide

These changes align with the v1.0.0 tree-shaking architecture where wagmi, Ethereum, and Solana utilities are separate subpath exports. The uiConfig prop and client.embeddedWallet.getEthereumProvider() pattern remain correct.