fix(visits): cap the window before a visit at the longest report

The window before a booked visit started at the last matching visit
however far back it lay, while the health-report export covers 730 days
and fell back to its 90-day default for anything longer. The card then
offered a report the export did not build. The window now stops at the
export's limit, read from one shared constant, and preparation.capped says
when it did; the web says "The last two years" for it.

The export clamps an over-long explicit range to the last 730 days before
its end instead of falling back to 90 days, so a custom range or a linked
window cannot shrink silently either, and its day count forgives the hour
a clock change adds, so two years of local days count as 730.

src/components/encounters/__tests__/visits-section.test.tsx

@@ -197,6 +197,7 @@ describe("<VisitsSection> since the last visit", () => {
       to: "2026-12-01",
       basis: "practitioner",
       since: sameDoctor,
+      capped: false,
     },
   });
   const unprepared = visit({ ...next, preparation: null });
@@ -346,6 +347,7 @@ describe("<VisitsSection> since the last visit", () => {
               to: "2026-12-01",
               basis: "default",
               since: null,
+              capped: false,
             },
           }),
         ],

src/components/encounters/preparation-text.ts

@@ -22,7 +22,10 @@ type Translate = (
 export interface PreparationText {
   /** Where the window starts: "Since your last visit with … on …". */
   title: string;
-  /** Why, when the title alone does not say: only on the default window. */
+  /**
+   * Why, when the title alone does not say: on the default window, and on a
+   * window capped at the longest report.
+   */
   reason: string | null;
 }
 
@@ -33,6 +36,14 @@ export function preparationText(
 ): PreparationText {
   const date = formatDay(preparation.from);
   const since = preparation.since;
+  // The matched visit is further back than a report covers: the window is
+  // the last two years, and the title must not promise everything since.
+  if (preparation.capped) {
+    return {
+      title: t("encounters.preparation.capped"),
+      reason: t("encounters.preparation.cappedReason"),
+    };
+  }
   switch (preparation.basis) {
     case "practitioner":
       return {