Implement Planner-Journal handoff (Group 9)

JWT-based handoff between Journal and Planner:

Journal side:
- JWT token generation scoped to route_id with 7-day expiry (jose)
- "Edit in Planner" button on route detail page — generates JWT,
  redirects to Planner /new with callback URL, token, and GPX
- Callback endpoint (POST /api/routes/:id/callback) validates JWT
  and creates new route version from received GPX

Planner side:
- /new route accepts callback, token, returnUrl, gpx params
- Creates session with callback metadata, initializes with GPX
- "Save to Journal" button POSTs GPX with Bearer token to callback
- "Return to Journal" link shown after successful save

All 6 Group 9 tasks complete.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/planner/app/routes.ts

@@ -2,6 +2,7 @@ import { type RouteConfig, index, route } from "@react-router/dev/routes";
 
 export default [
   index("routes/home.tsx"),
+  route("new", "routes/new.tsx"),
   route("api/sessions", "routes/api.sessions.ts"),
   route("api/route", "routes/api.route.ts"),
   route("session/:id", "routes/session.$id.tsx"),