Add e2e tests for Planner callback → geometry stored atomically

Introduces two E2E=true-gated test endpoints:
- POST /api/e2e/seed — creates a test user + bare route, returns routeId + JWT
- GET /api/e2e/route/:id — returns { hasGeom } for post-callback assertions

Three new integration tests:
- valid GPX via callback stores geometry (hasGeom = true)
- invalid GPX (< 2 track points) returns 400, geometry not stored
- missing token returns 401

CI: E2E=true added to the "Run E2E tests" step so the seed endpoints
are enabled when react-router-serve runs during the Playwright job.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -231,6 +231,7 @@ jobs:
         run: pnpm test:e2e
         env:
           BROUTER_URL: http://localhost:17777
+          E2E: "true"
 
       - name: Playwright job summary
         if: ${{ !cancelled() }}