i18n(pt-BR): add translations for newly added UI items + consistency pass

New pt-BR translations for items introduced in the latest releases, plus a consistency/quality pass across existing strings (grammar, tone, capitalization, pluralization). Placeholders and hotkeys preserved. No logic changes.

Pull Request Checklist

First-time contributor note acknowledged.

• Target branch: PR targets dev.
• Description: Included (see above and changelog).
• Changelog: Entry provided below following Keep a Changelog.
• Documentation: N/A (translation-only change; no docs impacted).
• Dependencies: None added/changed.
• Testing: Manual validation performed (see steps below).
• Code review: Self-review done; keys unchanged; JSON validated.
• Prefix: i18n used in title.

Changelog Entry

Description

Add missing pt-BR strings for new UI items introduced recently and refine existing translations for clarity and consistency. Improves UX for Brazilian Portuguese users; zero impact on application logic.

Added

• New pt-BR strings for recently introduced menus, tooltips, settings, and notifications.

Changed

• Standardized tone (second-person “você”), capitalization, and punctuation.
• Improved clarity of error/success messages and helper texts.
• Harmonized terminology (e.g., Model → Modelo, Context window → Janela de contexto, Workflow → Fluxo de trabalho).
• Preserved and repositioned placeholders where needed to fit natural pt-BR order.

Deprecated

• N/A

Removed

• N/A

Fixed

• Minor typos, inconsistent pluralization, and stray whitespace in several strings.
• A few ambiguous translations replaced with domain-accurate wording.

Security

• N/A

Breaking Changes

• None. No keys renamed or removed; only values adjusted.

Testing

How to validate

1. Go to Settings → Language and select Português (Brasil).

2. Smoke test key areas affected by recent changes:

   • Settings (general/models/privacy/import/export)
   • Workflows/Executions
   • Playground and Prompt helpers/tooltips
   • Conversations/History (bulk actions, confirmations)

3. Trigger both error and success states (e.g., invalid inputs, completed actions) to review messaging.

4. Verify placeholders like {name}, {count} and keyboard shortcuts render correctly.

Local checks performed

• JSON lint and build pass.
• Visual verification of long labels to avoid overflow/cut-off.
• No layout regressions observed on common screens.

Additional Information

• Scope limited to i18n files (pt-BR locale).
• If maintainers prefer a style guide for pt-BR (capitalization for buttons, confirmation tone, etc.), I can submit a follow-up PR with a concise glossary and conventions.

Screenshots or Videos

• (Optional) I can attach screenshots of key screens upon request.

Contributor License Agreement

By submitting this pull request, I confirm that I have read and fully agree to the [Contributor License Agreement (CLA)] (https://github.com/open-webui/open-webui/blob/main/CONTRIBUTOR_LICENSE_AGREEMENT), and I am providing my contributions under its terms.