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/en.json

@@ -200,6 +200,18 @@
 		"incomplete": "Calculation stopped before all quality stages completed.",
 		"cancel": "Cancel",
 		"cancelling": "Cancelling…",
+		"progress": {
+			"stages": {
+				"preparation": "Preparing the calendar",
+				"validation": "Checking your inputs",
+				"obligations": "Satisfying obligations",
+				"expiry": "Using balances that expire first",
+				"dates": "Settling the final dates"
+			},
+			"rule": "Applying “{rule}”",
+			"remaining": "About {value} {unit} left",
+			"overrun": "Taking longer than expected"
+		},
 		"cancelled": "Calculation cancelled",
 		"cancelledPartial": "Calculation cancelled — partial plan",
 		"error": "The planner encountered an unexpected error.",