feat(i18n): add complete Brazilian Portuguese (pt-BR) support

[roxi3906]

Summary

• add complete Brazilian Portuguese (pt-BR) localization across renderer and native Electron surfaces, locale persistence, update metadata, CI ownership, documentation, and release notes
• merge the latest main through 2a3cc5d3 and resolve conflicts while preserving the newly added German locale and every other translated locale
• translate every user-visible renderer string introduced by the v0.24.0 work with idiomatic Brazilian Portuguese and binding project terminology

Localization scope

• keep exact key parity across all namespaces: 33 common, 57 native, and 4,100 renderer entries
• add 167 renderer translations introduced by the latest main and remove 19 obsolete entries that no longer have call sites
• cover Notebook network protection and domain approvals, device-wide Connector credentials, OAuth and credential editors, trusted browsers, onboarding checks, project deletion and retained workspaces, Memory state, and Codex transport selection
• preserve Notebook, kernel, technical identifiers, interpolation placeholders, and Brazilian Portuguese CLDR one, many, and other categories
• update the Brazilian Portuguese README for v0.24.0 and add native Brazilian Portuguese v0.24.0 release notes
• update locale navigation, contribution guidance, glossary rules, version manifests, settings persistence, and CI language matrices for the combined de and pt-BR result

Validation

• focused locale, manifest, settings, CI, renderer, Notebook network, credential, onboarding, and deletion suite: 17 files, 1,479 / 1,479 passed
• localization resource guard: 1,126 / 1,126 passed
• npm run build: passed, including TypeScript checks, Electron build, and Web build
• npm run lint: passed
• targeted Electron E2E: 3 / 3 passed, covering the Brazilian Portuguese native quit dialog, German conflict regression, and the 640 px Brazilian Portuguese switch/restart flow without clipping
• Prettier, catalog key parity, conflict-marker, git diff --check, and clean-worktree checks: passed

Review

• independent read-only review covered translation semantics, destructive safety copy, glossary consistency, plural and placeholder integrity, locale registration, documentation accuracy, and Conventional Commits
• all findings were fixed; the final re-review reported no remaining Critical, Important, or Minor issues and marked the branch ready to merge

Notes

• the production build continues to emit existing non-blocking bundle-size, dynamic-import, CSS ::highlight, and third-party eval warnings