polish(detail): TODO review — calendar intro, drop abundance, collapse seed-saving

From the owner's TODO.org review of the shipped features:
- Crop calendar now says the months are YOUR notes: a hint line in the
  editor (cropCalendar.editorHint) and a caption under the 'this month'
  screen (calendar.selfNote) — it read as if the app knew when to sow.
- Dropped the 'how much I have' (abundance) input + display: it competed
  with the lot quantity as a second 'how much'. Removed from the lot sheet
  and the lot summary; the DB column + backup/CSV/catalog plumbing stay
  dormant (no destructive migration). offer_status carries 'do I share'.
- Seed-saving guidance moved into a collapsed expander (detail.seedSaving)
  — reference facts about the species shouldn't sit open among the
  grower's own records; opt-in depth, per progressive disclosure.
- Condition checks already live behind the collapsed 'advanced' expander
  (seed lots only) — left as the discreet power-user surface.

Tests: dropped the obsolete abundance→share nudge test; the seed-saving
section test now expands before asserting. analyze clean; suites green.

apps/app_seeds/lib/ui/calendar_screen.dart

@@ -71,6 +71,13 @@ class _CalendarScreenState extends State<CalendarScreen> {
             month: _month,
             onSelect: (m) => setState(() => _month = m),
           ),
+          Padding(
+            padding: const EdgeInsetsDirectional.fromSTEB(16, 0, 16, 8),
+            child: Text(
+              t.calendar.selfNote,
+              style: const TextStyle(color: seedMuted, fontSize: 12),
+            ),
+          ),
           const Divider(height: 1),
           Expanded(
             child: StreamBuilder<List<CalendarEntry>>(