docs(pt-br): add Brazilian Portuguese v5 documentation

[rodri-oliveira-dev]

Summary

• Adds a complete Brazilian Portuguese (pt-BR) translation of the Bounded Context Canvas v5 documentation.
• Updates the main README translation section with explicit links for French resources, existing Portuguese visual resources, and the new pt-BR documentation.
• Preserves the existing translations/pt/resources path and all current links for compatibility.
• Reuses the current v5 images, templates, and editable resources without modification.
• Preserves relevant English labels in parentheses so readers can match the translated documentation to the original visual resources.

Existing Portuguese resources

The existing Portuguese visual resources under translations/pt/resources remain unchanged and accessible.

The new textual documentation is added under translations/pt-br/README.md and points to the current v5 resources from the repository root. This keeps the contribution focused on documentation while avoiding a breaking migration of the existing assets.

Terminology

• Preserves official names such as Bounded Context Canvas, Domain-Driven Design, Core Domain Charts, Context Mapping, Wardley Maps, and DDD Toolbox.
• Translates established concepts while retaining the original English term on first occurrence where useful, including Bounded Context, Purpose, Strategic Classification, Domain Roles, Inbound Communication, Outbound Communication, Ubiquitous Language, Business Decisions, Assumptions, Verification Metrics, and Open Questions.
• Uses established pt-BR DDD terminology consistently with the other Brazilian Portuguese contributions to DDD Crew repositories.

Files

• README.md
• translations/pt-br/README.md

Validation

• Confirmed that the branch is one commit ahead of main and has no missing upstream commits.
• Confirmed that the main README diff is limited to the translation links.
• Verified relative links to the v5 canvas image, blank template, examples, worksheets, Miro backup, and tool-specific documentation.
• Preserved the existing French and Portuguese resource links.
• Confirmed that no duplicate pt-BR pull request exists.

Closes #58