Fix Timeline export and import round trips

[stef-k]

Summary

• emit standard lowercase GeoJSON structure while preserving Wayfarer property names
• accept bounded PascalCase aliases from earlier mobile exports
• parse complete quoted CSV records, including multiline Notes
• preserve existing duplicate, merge, and local-only Timeline behavior
• clarify that Timeline transfer is not a complete device backup

Closes #243

Validation

• focused production-service round trips: 4 passed, 0 failed, 0 skipped
• ordinary non-Android suite: 1,829 passed, 0 failed, 0 skipped
• Release build: succeeded, 0 errors
• git diff --check: passed
• Android/iOS builds not run because no platform-dependent files changed

Data and migrations

No database migration or synchronization change. Imported entries remain local-only; queue contents and other application state are excluded.

[github-actions]

Package	Line Rate	Branch Rate	Complexity	Health
WayfarerMobile.Core	83%	78%	611	✔
Summary	83% (846 / 1014)	78% (392 / 502)	611	✔