docs(api): sync fx-account spec with web source (#27)

* docs(api): sync fx-account spec with web source

Aligns apis/fx-account/openapi.yml with the live request/response shapes
exposed by fx-account's /api channel:

- POST /api/accounts: drop AssetRequest.isVirtual (not in source); add
  CompanyOwnerRequest.isStartup; rewire industry to a shared Industry
  schema regenerated from IndustryV2 (87 values).
- POST/PATCH /api/accounts/{id}/ubos: add phone, email, and
  isLegalRepresentative to UBORequest, UpdateUBORequest, and UBOResponse.
- GET /api/accounts/{id}/ubos: drop spurious pagination/filter params;
  response is a plain array, not a paginated envelope.
- GET /api/accounts/{id}/fundingInstructions: drop pagination/filter
  params, add asset and rail query filters, response is a plain array.
  FundingInstructionResponse now uses type as discriminator, exposes
  both type and rail fields, and includes the missing
  PIX_BANK_INSTRUCTION variant.
- Remove the /api/accounts/{id}/balances endpoint and associated
  schemas/examples/navigation entry — the route does not exist in
  fx-account.
- Rewrite RequirementResponse as a oneOf with five concrete variants
  (ACCOUNT_DOCUMENT, UBO_DOCUMENT, IDENTITY_VERIFICATION, ACCOUNT_FIELD,
  UBO_FIELD) matching the sealed class hierarchy.
- AssetResponse.asset renamed to currency to match the wire format.
- Extend DocumentType with KYC_FORM, BAAS_ADHESION_FORM,
  PJ_PARTNER_DOCUMENTS, PJ_PARTNER_FINANCIAL_STATEMENT, and
  SIGNING_AUTHORITY_PROOF.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* fix(openapi): unwrap RequirementResponse description intro line

The text-formatting eval flagged a soft-wrapped line inside a `|`
literal block, where the newline renders as a visible break in
Mintlify. Joining the intro sentence keeps the bullet list intact.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

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Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: leonisandes