docs: add TON Connect integration guide for apps

[devin-ai-integration]

Summary

Adds a new documentation guide for integrating WalletConnect into TON Connect applications. The guide covers prerequisites (project ID, existing TON Connect project), package installation, and usage with the initializeWalletConnect() function.

The guide is added to the Apps tab under the "Guides" section in the navigation.

Review & Testing Checklist for Human

• Verify API accuracy: Confirm that initializeWalletConnect is actually exported from @tonconnect/sdk and accepts the parameters shown in the examples
• Verify package names: Confirm @reown/appkit-universal-connector exports UniversalConnector as documented
• Check preview deployment: Verify the new guide renders correctly and appears in the navigation under Apps > Guides > TON Connect
• Review code examples: Ensure the example implementation pattern (initialize WalletConnect before TonConnect instance) is correct

Test Plan

1. Navigate to the preview deployment
2. Go to Apps tab and verify "TON Connect" appears under Guides
3. Click through and verify all sections render properly (Prerequisites, Installation, Usage)
4. Verify code blocks have proper syntax highlighting

Notes

The code examples in this guide were provided by the requester. Since this is a documentation-only change with no automated tests, manual verification of API accuracy is important.

Link to Devin run: https://app.devin.ai/sessions/843a87d46c3a401e9f14155d24fe6680
Requested by: [email protected]

[devin-ai-integration]

🤖 Devin AI Engineer

I'll be helping with this pull request! Here's what you should know:

✅ I will automatically:

• Address comments on this PR. Add '(aside)' to your comment to have me ignore it.
• Look at CI failures and help fix them

Note: I can only respond to comments from users who have write access to this repository.

⚙️ Control Options:

• Disable automatic comment and CI monitoring