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/20261028231042668-routes/migration.json

@@ -0,0 +1,94 @@
+{
+  "__className__": "serverpod.DatabaseMigration",
+  "actions": [
+    {
+      "__className__": "serverpod.DatabaseMigrationAction",
+      "type": "createTable",
+      "createTable": {
+        "__className__": "serverpod.TableDefinition",
+        "name": "route",
+        "dartName": "SavedRoute",
+        "module": "halkyon_train",
+        "schema": "public",
+        "columns": [
+          {
+            "__className__": "serverpod.ColumnDefinition",
+            "name": "id",
+            "fieldName": "id",
+            "columnType": 7,
+            "isNullable": false,
+            "columnDefault": "random_v7",
+            "dartType": "UuidValue?"
+          },
+          {
+            "__className__": "serverpod.ColumnDefinition",
+            "name": "spaceId",
+            "fieldName": "spaceId",
+            "columnType": 6,
+            "isNullable": true,
+            "dartType": "int?"
+          },
+          {
+            "__className__": "serverpod.ColumnDefinition",
+            "name": "keyId",
+            "fieldName": "keyId",
+            "columnType": 0,
+            "isNullable": true,
+            "dartType": "String?"
+          },
+          {
+            "__className__": "serverpod.ColumnDefinition",
+            "name": "payload",
+            "fieldName": "payload",
+            "columnType": 5,
+            "isNullable": false,
+            "dartType": "dart:typed_data:ByteData"
+          },
+          {
+            "__className__": "serverpod.ColumnDefinition",
+            "name": "nonce",
+            "fieldName": "nonce",
+            "columnType": 5,
+            "isNullable": true,
+            "dartType": "dart:typed_data:ByteData?"
+          }
+        ],
+        "foreignKeys": [
+          {
+            "__className__": "serverpod.ForeignKeyDefinition",
+            "constraintName": "route_fk_0",
+            "columns": [
+              "spaceId"
+            ],
+            "referenceTable": "offline_sync_spaces",
+            "referenceTableSchema": "public",
+            "referenceColumns": [
+              "id"
+            ],
+            "onUpdate": 3,
+            "onDelete": 4
+          }
+        ],
+        "indexes": [
+          {
+            "__className__": "serverpod.IndexDefinition",
+            "indexName": "route_space_idx",
+            "elements": [
+              {
+                "__className__": "serverpod.IndexElementDefinition",
+                "type": 0,
+                "definition": "spaceId"
+              }
+            ],
+            "type": "btree",
+            "isUnique": false,
+            "isPrimary": false
+          }
+        ],
+        "managed": true
+      }
+    }
+  ],
+  "warnings": [],
+  "migrationApiVersion": 1
+}