docs(pt-br): add Brazilian Portuguese translation

[rodri-oliveira-dev]

Summary

• Adds a Brazilian Portuguese (pt-BR) translation of the main Core Domain Charts documentation.
• Translates the First-to-Market Core and Pioneers Run Experiments examples.
• Translates the Draw.io template usage instructions.
• Adds a link to the pt-BR documentation in the main README.

Terminology

• Preserves official names such as Core Domain Chart, Team Topologies, Wardley Mapping, and First-to-Market Core.
• Translates established DDD concepts while retaining the original English term on first occurrence where useful, such as Core Domain, Bounded Context, Model Complexity, and Business Differentiation.
• Retains English labels in parentheses when they correspond to labels displayed in the original diagrams or Draw.io interface.

Visual resources

The existing diagrams and editable Draw.io template are intentionally reused without modification and remain in English.

Each translated document includes a note explaining this approach so readers can correlate the Portuguese text with the original visual labels.

Files

• translations/pt-br/README.md
• translations/pt-br/examples/first-to-market-core.md
• translations/pt-br/examples/pioneers-run-experiments.md
• translations/pt-br/resources/drawio-template/readme.md
• README.md

Validation

• Compared the translation branch with main.
• Confirmed that only documentation files were added or updated.
• Verified the relative paths to the reused visual resources.
• No automated tests are applicable to this documentation-only change.

Closes #23