refactor: use the SDK personal IBAN contract

[TaprootFreak]

Consumer side of step 1 of DFXswiss/packages#198: use the personal IBAN contract from
@dfx.swiss/react and drop the local copies.

Depends on DFXswiss/packages#199.

Changes

• src/dto/virtual-iban.dto.ts and src/hooks/virtual-iban.hook.ts are gone; VirtualIban and
  useVirtualIban now come from the package.
• The generic selector helpers (normalizePersonalIban, toPersonalIbanProviderRequest,
  isUnrecognizedPersonalIbanSelector) are gone from src/util/personal-iban.ts and are imported
  from the package instead. isExplicitFrickPersonalIbanRequest stays local and is now built on the
  package's toPersonalIbanProvider.
• The feature-specific parts stay where they are: error copy, the currency/payment-method
  applicability rule, the response check against a specific bank and account holder, and the URL and
  widget parameter handling.
• The suites that replace @dfx.swiss/react with a hand-written object need the four selector
  helpers in that object. src/test-utils/personal-iban-sdk-mock.ts holds them once instead of
  restating them in each of the five affected suites.
• The selector tests that only exercised those helpers are dropped here — they now live with the
  implementation, in the package.

Before this can go green

The package pin in package.json still points at the published @dfx.swiss/react, which does not
export useVirtualIban, VirtualIban or the selector helpers yet. CI stays red until
DFXswiss/packages#199 is merged and published and the pin is raised here. That is the only thing
missing — verified locally against a build of that branch: tsc clean, npm run lint clean, and
the full suite at 667 passing with no new failures (the two suites failing on develop today still
fail, unchanged).

[github-actions]

🤖 PR Review Bot

❌ TypeScript: 8 errors

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