* feat(export): separate resume/cover-letter downloads, redesign dialog, add Markdown
Let people export the resume and cover letter as distinct documents, and add a
Markdown format alongside PDF / DOCX / JSON (handy for AI agents).
- Server/API: scope PDF generation and download URLs to a resume/cover-letter target.
- Export domain: getResumeExportData + resumeHasCoverLetter in @reactive-resume/resume.
- Redesign the download dialog: one global "What to export" scope toggle (Tabs) plus
flattened per-format rows, reusing existing UI components and design language.
- Add Markdown export (@reactive-resume/resume/markdown) with a small tiptap-HTML converter.
- Fix blank section headings in DOCX and Markdown by injecting the locale-aware
section-title resolver (titles are stored empty and resolved at render time).
- Locale catalogs updated for the new strings.
* test(e2e): open the download dialog before exporting JSON
The JSON export moved into the redesigned download dialog, so the spec now opens
the dialog from the Export sidebar section before clicking "Download JSON".
Amruth Pillai