Add Trip Editor area editing

[stef-k]

Closes #248

Summary

• Added Trip Editor area create/update/delete/order API endpoints.
• Added deterministic area parsing/validation and GeoJSON Polygon handling.
• Added mutation envelopes for affected.areas, affected.areaOrdersByRegionId, and deletedIds.areas.
• Added area rows/forms under regions with docked/expanded shared surfaces.
• Added shared map-work polygon draw/edit using repo-local Leaflet.Draw assets.
• New areas draw a polygon with L.Draw.Polygon; existing area polygons edit through Leaflet.Draw edit mode.
• Done writes draft geometry only and does not save.
• Normal Save persists through area create/update endpoints.
• Area reorder uses drag handles and complete region area order.

Scope exclusions

• no geocode/search-add
• no place coordinate changes
• no marker drag
• no segment editing
• no final cutover
• no legacy editor behavior changes
• no Quill/rich text parity
• no visible Save Geometry UI

Validation

• dotnet build passed, existing ASP0000 warning only
• dotnet test tests/Wayfarer.Tests/Wayfarer.Tests.csproj --filter TripEditor passed, 108 tests
• full dotnet test passed earlier in the branch, 1539 tests, before the Leaflet.Draw fix; not rerun after final fix
• npm run build passed
• npx playwright test --config=playwright.config.ts --list passed, 42 tests listed
• npm run test:e2e:trip-editor was not runnable locally because ASP.NET was unavailable at http://localhost:5012
• LOC checker passed with accepted warnings for styles.css and MetadataEditor.vue
• rg "window\.confirm" no matches
• rg "\bconfirm\(" reviewed shared confirm usages only
• git diff --check origin/main...HEAD passed

Testing note

Backend tests cover area API success, validation, forbidden fields, geometry-only endpoint, and order invalid IDs.

Playwright coverage added for area add/edit/reorder/map-work/expanded/dirty-confirmation/out-of-scope absence, but runtime E2E still needs GitHub or local dev server execution.

[stef-k]

Final pre-merge check after ec571bd:

• No blocking findings remain after ec571bd67e52803387c6d0f0a067fc54a646d4ef.
• GitHub checks passed (test).
• Final local E2E rerun was not possible because the required ASP.NET and Vite servers were unavailable.
• Scope remained area CRUD/order/polygon map-work only.
• Deferred scope remains geocode/search-add, place coordinate changes, marker drag, segment editing, final cutover, legacy cleanup, and Quill parity.