Merge branch 'train-days' into integration

# Conflicts:
#	apps/train/halkyon_train_flutter/lib/src/app/train_paths.dart
#	docs/adr/0030-halkyon-train.md

apps/train/halkyon_train_server/lib/src/weight/body_weight.spy.yaml

@@ -0,0 +1,19 @@
+### A weight the person measured (ADR 0030, D64): when, how heavy and where
+### it came from (entered in Train, or read from Health Connect with that
+### record's ID, so that it is read once), in its sealed payload (D7); the
+### instance sees that it exists, its size and when it changed. A row each
+### measurement. Synced.
+class: BodyWeight
+table: body_weight
+database: sync
+fields:
+  ### The key it is sealed with (ADR 0002's envelope); never null in Train.
+  keyId: String?
+  ### The content, sealed: UTF-8 JSON with a `schemaVersion` once opened.
+  payload: ByteData
+  ### The sealing's nonce (ADR 0002's envelope).
+  nonce: ByteData?
+indexes:
+  # Deleting a space finds its rows through this index (see content_key).
+  body_weight_space_idx:
+    fields: spaceId