feat(app): reviews know how a card was studied; progress can start afresh

Each review records its mode (ADR 0004, rule 3): front to back, back to
front with a schedule of its own, or crammed outside the schedule. A
card's schedule replays only the reviews of one mode. Resetting progress
appends a 'reset' entry per card, no migration (the column is text):
schedules replay what follows it, and the history stays for the streak
and the heatmap. Reviews are inserted in batches.

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

halkyon_learn_server/lib/src/review/review_log.spy.yaml

@@ -20,6 +20,8 @@ fields:
   ### (back to front, with a schedule of its own, as Anki's reverse cards have),
   ### or 'cram' (outside the schedule: counts for streaks and the activity
   ### heatmap, never moves a schedule). Reviews from before modes are 'review'.
+  ### 'reset' is no rating but a fresh start: the card's schedules replay only
+  ### what follows it, its rating means nothing.
   mode: String, default='review'
 indexes:
   # Deleting a space finds its rows through this index (see studyset.spy.yaml).