Warn when saving unevenly costs the family days

Only ninety-six days survive a child's fourth birthday, and with two parents
that is forty-eight each rather than a shared pool. A parent sitting on sixty
days while the other has ten therefore forfeits twelve that the family could
have kept, and nothing said so.

The advice leads with taking the days as leave before the birthday, which
turns them into actual time at home, and offers transferring only as the
fallback that merely preserves them. The transferable figure is bounded by
what Försäkringskassan actually reports as transferable, since the reserved
days cannot move, and the copy says plainly that a transfer happens there and
not in this app. Without the partner's figures the tip hedges rather than
inventing a number.

frontend/src/i18n/en/tips.ts

@@ -1,4 +1,10 @@
 export const tips = {
+  'tip.age4PoolingLossExact.body':
+    '{surplus_parent} has {excess_days} more days left than may be saved per parent at the child\'s 4th birthday ({fourth_birthday}) — otherwise the family loses {family_loss_days} days. Taking that leave before then is best, since it turns entitlement into actual time at home. If that\'s not possible, you can transfer up to {transfer_days} days to {lagging_parent} at Försäkringskassan instead — that saves the days but doesn\'t add any extra time off, and the transfer itself happens at Försäkringskassan, not in this app.',
+  'tip.age4PoolingLossExact.title': 'Uneven saving costs the family days',
+  'tip.age4PoolingLossHedged.body':
+    '{surplus_parent} has {excess_days} more days left than may be saved per parent at the child\'s 4th birthday ({fourth_birthday}). Taking that leave before then is best, since it turns entitlement into actual time at home. If you both have days left, you can otherwise transfer days between you at Försäkringskassan — that saves the days but doesn\'t add any extra time off, and the transfer itself happens at Försäkringskassan, not in this app.',
+  'tip.age4PoolingLossHedged.title': 'Uneven saving may cost the family days',
   'tip.aria': 'Tip: {title}',
   'tip.balanceBetweenParents.body': '{leading_parent} has taken {gap_days} more days than {lagging_parent}. Consider evening out the split.',
   'tip.balanceBetweenParents.title': 'Imbalance between parents',