feat(leave) : align forfait CP N + display remaining workdays + N-1 absences exempt from presence

- LeaveRecapRowBuilder: forfait CP N now reflects remainingDays (acquis − pris depuis N) instead of the constant acquiredDays. Affects both PDF export and screen recap.
- Employee detail header: forfait label becomes "Forfait - 218 jours (X restants)" where X = 218 − presence days from Jan 1 to today (today included).
- New EmployeeLeaveSummary.presenceDaysToToday field, computed via the same logic as presenceDaysByMonth but capped at today.
- Forfait business rule: leaves attributed to N-1 stock no longer decrement presence days. Implemented by chronologically consuming an N-1 budget (= previousYearTakenDays) inside computePresenceDaysByMonth before counting any absence. Non-forfait unaffected (budget is 0).
- Doc updates: CLAUDE.md (forfait/N-1 rule), functional-rules.md (CP N forfait semantics).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/Service/Leave/LeaveRecapRowBuilder.php

@@ -73,7 +73,7 @@ final readonly class LeaveRecapRowBuilder
                         }
                     }
                     $cpN1Remaining     = round($yearSummary['previousYearRemainingDays'], 2);
-                    $cpN               = (string) round($yearSummary['acquiredDays'], 2);
+                    $cpN               = (string) round($yearSummary['remainingDays'], 2);
                     $acquiredSaturdays = '-';
                 } else {
                     $cpN1Remaining     = round($yearSummary['remainingDays'], 2);