feat(planning): follow the indicative wait in calculation progress

The overlay percentage now rises linearly to 95% at the expected wait
captured at Calculate, holds there, and shows 100% only when the planner
completes. Beneath the status, one line names the current planning stage
(with the rule name for rule stages) and another shows the approximate
remaining time, or "Taking longer than expected" once the wait is
exceeded, announced once through the live status. Cancel freezes the
percentage and hides both lines.

PlanningCalculationService reports the stage and submitted request
instead of fixed per-stage percentages; PlanningDurationService owns the
wait progress on a 250 ms tick.

Closes #300

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/i18n/fr.json

@@ -200,6 +200,18 @@
 		"incomplete": "Le calcul s’est arrêté avant la fin des critères de qualité.",
 		"cancel": "Annuler",
 		"cancelling": "Annulation en cours…",
+		"progress": {
+			"stages": {
+				"preparation": "Préparation du calendrier",
+				"validation": "Vérification de vos saisies",
+				"obligations": "Respect des obligations",
+				"expiry": "Utilisation des soldes qui expirent en premier",
+				"dates": "Fixation des dates définitives"
+			},
+			"rule": "Application de « {rule} »",
+			"remaining": "Encore environ {value} {unit}",
+			"overrun": "Plus long que prévu"
+		},
 		"cancelled": "Calcul annulé",
 		"cancelledPartial": "Calcul annulé — plan partiel",
 		"error": "Le planificateur a rencontré une erreur inattendue.",