fix(visits): open an upcoming appointment where it lives

Visits are the second tab of `/checkups`, and the bare path opens the
first one, the preventive-care list, which never shows an appointment.
Every surface that listed an upcoming appointment linked it there: the
dashboard's next-appointment line, the Today rail item, the Today
overview fact and the appointment's push notification. A tap on the
appointment landed on the list it is not on.

Each now opens the visit itself (`/checkups?visit=<id>`), or the visits
tab (`/checkups?view=visits`) for a line naming several appointments.
The checkups page reads `view` to pick a tab. The rail item stops
borrowing the check-up item's action: it carries its own label
("View appointment") and intent `visit.view`. The appointment push names
its visit through the producer's `metadata.url` override; a check-up's
push keeps the checkups list.

The same mis-route sat on three links that lead to visits without
being upcoming: a condition's visit rows, the address book's back link
and the onboarding and timeline prompts to add a visit.

`visit-link-guard.test.ts` keeps the visit paths in the builder and
counts every bare `/checkups` per file, each with the reason it names
the checkups list.

src/components/practitioners/practitioner-list.tsx

@@ -39,6 +39,7 @@ import {
   usePractitioners,
   type Practitioner,
 } from "@/hooks/use-practitioners";
+import { VISITS_PATH } from "@/lib/encounters/visit-links";
 import { useTranslations } from "@/lib/i18n/context";
 import { PractitionerSheet } from "./practitioner-sheet";
 
@@ -107,7 +108,7 @@ export function PractitionerList({ enabled = true }: { enabled?: boolean }) {
       <PageHeader
         title={t("practitioners.title")}
         description={t("practitioners.description")}
-        backLink={{ href: "/checkups", label: t("encounters.sectionTitle") }}
+        backLink={{ href: VISITS_PATH, label: t("encounters.sectionTitle") }}
         actions={addButton}
       />