fix(sections-editor): translate rich-text toolbar aria-labels

[pedrofrxncx]

Follows the repeated i18n hardening lane (#5099, #5321, #5348, #5369, #5373, #5377, #5433, #5446, #5465, #5477, #5479, #5487).

RichTextField's toolbar has 14 ToolbarButtons that pass label straight through to aria-label. 4 of them (font-size inc/dec, style dropdown) already go through t(), but the other 10 — bold, italic, underline, strikethrough, bullet list, ordered list, align left/center/right, justify — were hardcoded English strings. pt-br users get untranslated labels on the toolbar's most-used buttons (screen readers announce English regardless of locale).

Fix: added the 10 missing keys to en/sections-editor.ts and pt-br/sections-editor.ts, and swapped each hardcoded label="..." for t("sectionsEditor.richTextField.<key>") in rich-text-field.tsx.

To confirm: grep -n 'label="' apps/web/src/components/sections-editor/fields/rich-text-field.tsx returns nothing (all labels now go through t()), and cd apps/web && bunx tsc --noEmit passes — the pt-br dictionary's satisfies Record<keyof typeof enDomain, string> constraint would fail to compile if any key were missing.

Locally ran: bun run fmt (no changes), cd apps/web && bunx tsc --noEmit (clean), bunx oxlint on the 3 changed files (0 warnings/errors). Full CI validates the rest.

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Summary by cubic

Localizes Rich Text toolbar aria-labels to fix untranslated buttons and improve screen reader output, especially for pt-br users.

• Bug Fixes
  • Replaced hardcoded labels for bold, italic, underline, strikethrough, bullet/ordered list, and align left/center/right/justify with t("sectionsEditor.richTextField.*").
  • Added the corresponding keys to en/sections-editor.ts and pt-br/sections-editor.ts.

^{Written for commit 5dc9ab9. Summary will update on new commits.}