feat(keychain): add identity verification for Stripe purchases

[broody]

Summary

• Adds identity verification step (first name, last name, phone number) for new users purchasing starterpacks via Stripe, using the accountVerify GraphQL mutation
• Gates Stripe checkout behind proveVerifiedAt check — verified users skip directly to payment
• Uses sandbox: !isMainnet to toggle between UAT and production Prove environments

Test plan

• Purchase starterpack via Stripe as a new (unverified) user — should show verification form before Stripe checkout
• Purchase starterpack via Stripe as a verified user — should skip directly to Stripe checkout
• Verify sandbox mode is used on Sepolia and production mode on mainnet
• Verify form validation (empty fields, invalid phone number)
• Verify error handling when accountVerify mutation fails

🤖 Generated with Claude Code

[vercel]

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Project	Deployment	Actions	Updated (UTC)
controller-example-next	Ready	Preview	Mar 16, 2026 8:09pm
keychain	Ready	Preview	Mar 16, 2026 8:09pm
keychain-storybook	Ready	Preview	Mar 16, 2026 8:09pm

[claude]

Claude finished @broody's task —— View job

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Documentation Update Complete

I've analyzed the PR and updated the documentation in the docs repository.

Changes Made

User-Facing Impact: This PR adds identity verification for Stripe purchases. New users must provide first name, last name, and phone number before completing checkout. Verified users skip directly to payment.

Documentation Updated:

• ✅ Added identity verification step (step 5) to the purchase flow in src/pages/controller/starter-packs.md
• Single canonical edit in the appropriate location following minimal update guidelines

Files Modified

docs-repo/src/pages/controller/starter-packs.md
+ 5. **Identity Verification** (Stripe only): First-time Stripe users must verify their identity by providing first name, last name, and phone number. Verified users skip directly to payment.

Next Steps

The documentation change has been made and staged in the cartridge-gg/docs repository. To complete the update:

1. Create a new branch in the docs repo
2. Commit the staged changes
3. Push and create a PR in the docs repository

The change is minimal, focused, and follows the documentation guidelines:

• ✅ Single canonical location (starter-packs.md)
• ✅ Minimal edit (one new step in the purchase flow)
• ✅ No duplication across multiple pages
• ✅ User-facing change warranted documentation update