fix(resume-import): parse non-English month names and ongoing markers

[Dwarf1er]

Summary

parseImportDate only understood English month names and the word "Present". For a non-English resume,
"janvier 2020" fails to parse and the start date silently becomes 2000-01-01, and "Présent" or
"actuel" is not recognised as ongoing. This makes date parsing locale-independent.

Changes

• New src/actions/resumeImport/dates.ts: month names for about 20 locales are built from Intl (long
  and short forms, accents folded) rather than hand-written lists. Names that mean different months in
  different locales are dropped as ambiguous.
• Also handles YYYY-MM, YYYY/MM, CJK year-month (2020年3月) and filler words (enero de 2020).
• Multilingual ongoing markers ("Présent", "actuel", "en cours", "Heute", "Actualidad", "現在", ...).
• parseImportDate in shared.ts uses the new helpers; existing formats (Jan 2020, 2020,
  MM/YYYY) behave as before.
• Resume import prompt: copy text values in their original language and never translate; map "ongoing"
  in any language to "Present".
• New __tests__/resumeImportDates.spec.ts (27 cases).

Related Issues

Testing

• npm run lint and tsc --noEmit are clean.
• New spec: 27 passing. The rest of the suite is unchanged: 193 tests fail identically on a clean dev
  in my environment (jsdom/localStorage setup), unrelated to this change.
• Not covered: the Intl month list depends on the runtime's ICU data, which is full in the Docker
  image's Node 20.

Notes

Independent of the language-output PR; either can merge first.