* feat(billing): add i18n pluralization support for billing unit names
Use i18next plural feature to properly translate and pluralize unit names
in billing plans (e.g., "member" vs "members"). This ensures correct
grammar for phrases like "Up to 4 members included in the plan" and
enables proper translation of unit names in non-English locales.
* fix(billing): handle 'unlimited' tier values in pluralization
Add getSafeCount helper to safely convert tier values to numbers,
preventing NaN when 'unlimited' values are passed to pluralization.
Falls back to plural form for 'unlimited' or invalid values.
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Co-authored-by: Claude <noreply@anthropic.com>
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