Improve Portuguese translations

[Blackspirits]

Description

This pull request improves the European Portuguese (pt) translations for clarity, natural phrasing, and consistency with the current MagicMirror² UI.

Changes

• Replace Sem eventos programados. with the more natural calendar wording Sem eventos agendados.
• Improve the client request error message.
• Improve the unspecified error message for more natural Portuguese.
• Reword the module update completion message.
• Improve the alert welcome message.
• Keep terminology and placeholders consistent with the English source and the current UI context.

No translation keys or placeholders were added, removed, or changed.

Related issue

No related issue.

Testing

• Compared all Portuguese translation entries against the corresponding English source files.
• Verified that all placeholders remain unchanged.
• Verified the translations in the context of the current calendar, weather, update notification, and alert modules.
• Ran node --run lint:fix.

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