3c: partial consumption + undo for cooking sessions

- Append-only undo via correction transactions tied to cookingSessionId.
- POST /v1/cooking-sessions/:id/undo with 24h UTC window (409 + i18n after expiry).
- Complete undo scope: meals removed, meal boxes discarded, recipe_cooks
deleted, cookCount decremented; activation milestones left intact.
- Deterministic assumption-profile rollback via lastSessionAnswers.sessionId;
profile deleted when observationCount reaches 0.
- New status 'undone' as TEXT validated against COOKING_SESSION_STATUSES.
- Analytics event cooking_session_undone + domain events MEAL_BOX_DISCARDED,
MEAL_REMOVED, COOKING_SESSION_UNDONE.
- Partial consumption uses actualPortionsEaten/plannedPortions factor.
- i18n coverage for cooked.undoWindowExpired across all 12 locales + server.
- Invariant tests: computeBalance(transactions) === item.quantity after
complete, undo, and undo + new complete; transaction count increases on undo.
- Migration 0014_expand_event_types.sql adds new enum values.
- Updated FAS3-COOKING-SESSIONS-AUDIT.md with chosen semantics.

packages/inventory-engine/src/cooking-profiles.ts

@@ -55,6 +55,51 @@ export function updateCookingAssumptionProfile(
   return { averageEatenPortions, averageLeftoverPortions, observationCount, lastSessionAnswers };
 }
 
+/**
+ * Återställ en antagandeprofil genom att ta bort ett specifikt sessions-id
+ * från historiken och räkna om medelvärdena deterministiskt från resterande
+ * observationer. Ren funktion – alla beroenden är explicita argument.
+ */
+export function rollbackCookingAssumptionProfile(
+  sessionId: string,
+  existing: ExistingProfile,
+): {
+  averageEatenPortions: number | null;
+  averageLeftoverPortions: number | null;
+  observationCount: number;
+  lastSessionAnswers: Array<{ sessionId: string; eaten: number; leftovers: number; date: string }>;
+} {
+  const history = (existing.lastSessionAnswers ?? []).filter((a) => a.sessionId !== sessionId);
+
+  if (history.length === 0) {
+    return {
+      averageEatenPortions: null,
+      averageLeftoverPortions: null,
+      observationCount: 0,
+      lastSessionAnswers: [],
+    };
+  }
+
+  // Räkna om EMA från scratch i kronologisk ordning (äldst först).
+  const chronological = [...history].reverse();
+  let avgEaten = chronological[0]!.eaten;
+  let avgLeftovers = chronological[0]!.leftovers;
+
+  for (let i = 1; i < chronological.length; i++) {
+    const alpha = 1 / (i + 1);
+    const a = chronological[i]!;
+    avgEaten = round2(avgEaten + alpha * (a.eaten - avgEaten));
+    avgLeftovers = round2(avgLeftovers + alpha * (a.leftovers - avgLeftovers));
+  }
+
+  return {
+    averageEatenPortions: avgEaten,
+    averageLeftoverPortions: avgLeftovers,
+    observationCount: history.length,
+    lastSessionAnswers: history,
+  };
+}
+
 function clamp(n: number, min: number, max: number): number {
   return Math.max(min, Math.min(max, n));
 }