feat(coach): extend the snapshot window enum with lastYear

Adds a year-in-review window between last90days and allTime so the
Coach drawer can ground a long-horizon question (seasonal mood
patterns, year-over-year weight trajectory) without falling back to
the unbounded `allTime` window. The new enum value flows through the
scope schema, the snapshot builder's window-to-day-count mapping,
the provenance window-set seeding so the source-chips render the
year-in-review chip, and the Coach source-chips Record.

Extends the snapshot test with a `lastYear`-specific assertion that
pins the scope window and the provenance envelope.

src/components/insights/coach-panel/source-chips.tsx

@@ -51,6 +51,10 @@ const WINDOW_KEYS: Record<CoachProvenance["windows"][number], string> = {
   last7days: "insights.coach.window.last7days",
   last30days: "insights.coach.window.last30days",
   last90days: "insights.coach.window.last90days",
+  // v1.4.27 B7 / BL-P6-4 — year-in-review window. The i18n key
+  // resolves to a localised label; absent translations fall back
+  // through the resolver to the English source.
+  lastYear: "insights.coach.window.lastYear",
   allTime: "insights.coach.window.allTime",
 };