Add Gmail/Outlook CSV contact import and export

[tomcardoso]

Summary

• CSV import now auto-detects Gmail's and Outlook's contact-export header shapes and remaps them onto Sourcerer's existing column vocabulary before the normal import logic runs. Plain Sourcerer-format CSVs are unaffected.
  • Gmail: supports both the current schema (First Name/Last Name, unprefixed Organization Name/Organization Title, numbered E-mail N - Value/Phone N - Value/Website N - Value) and an older export variant (Given Name/Family Name, Organization 1 - Name/Title). Verified against Google's own current contacts import template.
  • Outlook: First Name/Last Name, up to 3 emails, 6 phone types, Web Page + Personal Web Page. Verified against a real Outlook contacts export.
  • LinkedIn/X URLs found in generic website columns are routed to their own contact_links type instead of landing in "website".
• Export gains two new formats, "Export as Gmail CSV" and "Export as Outlook CSV", available from both the All Contacts view and per-project export menus, alongside the existing CSV/Excel and vCard options.
  • Gmail export dynamically widens E-mail N - Value/Phone N - Value/Website N - Value to fit however many the widest contact in the export actually has — nothing is dropped, matching Google's genuinely unbounded numbered-column schema.
  • Outlook export fills all of Outlook's real fixed slots (3 emails, 6 phone types, 2 web pages) — the true ceiling of that schema, since Outlook has no expandable numbering scheme the way Gmail does.
• After a CSV import, the result modal now notes any source columns that carried data but have no home in Sourcerer's contact model (e.g. physical addresses, spouse, custom fields) so nothing silently vanishes without the user knowing. Type/Label companion columns (e.g. Phone 1 - Type) are excluded from that note since they're just qualifiers on data that was imported.
• Birthdays are normalized between ISO (YYYY-MM-DD), Google's year-unknown form (--MM-DD, discarded), and Outlook's M/D/YYYY.

Test plan

• npm run typecheck passes
• npm test passes (547 tests), including src/test/csv-format-detection.test.ts (Gmail/Outlook detection, both schema variants, dropped-field reporting, end-to-end import) and cases in src/test/export.test.ts (Gmail/Outlook export shape, dynamic widening, fixed Outlook slots)
• Manual testing in the running dev app against real Gmail and Outlook contact export files

Closes #463