feat(train): routes kept as sealed rows, planned on the map (ADR 0030, D44)

Routes are synced `route` rows (the model `SavedRoute`, as Flutter has a
`Route`), sealed as plans are; the migration `routes` only creates the
table, its space index and its cascade to the sync engine's spaces. A
route's payload holds its name, activity, profile, waypoints and the way
planned, points and elevations delta-coded and gzipped.

Home gets a fourth tab, Routes, and the planner: waypoints tapped on the
map, held and dragged, the last undone, a new route's first where the
phone is (GPS through the recorder's channel), the way planned by the
instance's BRouter after each change, an earlier answer dropped; its
distance, climb, descent, elevation and surfaces under the map.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

apps/train/halkyon_train_client/lib/migrations/migration_registry.dart

@@ -8,6 +8,7 @@ part '20261028101012641-workouts/migration.dart';
 part '20261028164640000-profile/migration.dart';
 part '20261028181405893-days/migration.dart';
 part '20261028211508606-plans/migration.dart';
+part '20261028231042668-routes/migration.dart';
 
 /// Migration registry for the client-side database.
 class MigrationRegistry {
@@ -18,6 +19,7 @@ class MigrationRegistry {
     _Migration20261028164640000_profile(),
     _Migration20261028181405893_days(),
     _Migration20261028211508606_plans(),
+    _Migration20261028231042668_routes(),
   ];
 
   /// List of all client-side database migration versions.