feat(payment-link): add urble wallet app

[joshuakrueger-dfx]

Summary

• Adds new wallet app urble to the payment link wallet list
• Supports Bitcoin and Cardano, deep link urble:
• Logo expected at https://dfx.swiss/images/app/urble.webp (separate landing-page change)

Test plan

• Migration runs without error against develop DB
• GET /v1/paymentLink/walletApp returns urble entry
• urble appears in "Other apps" section on /pl pages
• Logo loads correctly once landing-page asset is deployed

[TaprootFreak]

Unsigned Commits

This PR contains 2 unverified commits. Please sign them before merge.

Quick fix with Claude

Paste this prompt into Claude Code:

My commits on branch feature/add-urble-wallet-app in DFXswiss/api are unsigned. 
Set up SSH commit signing for me if not already configured, then re-sign all 
unsigned commits on this branch and force-push.

Manual fix

# 1. Set up SSH signing (if not already done)
git config --global gpg.format ssh
git config --global user.signingkey ~/.ssh/id_ed25519.pub
git config --global commit.gpgsign true

# 2. Re-sign commits (rebase on develop)
git checkout feature/add-urble-wallet-app
git rebase --exec 'git commit --amend --no-edit -S' develop

# 3. Push
git push --force-with-lease