i18n: convert feature pages, dialogs, auth sub-pages and nav to t()

Move all hardcoded UI strings in the appointments, prescriptions, tasks,
messages, activity, analysis and patients views (plus their dialogs and
detail sheets), the remaining auth pages (verify-email, forgot/reset
password, accept-invite, onboarding), the clinic form and the sidebar user
menu into i18next keys in en/translation.json. Clinical option values
(appointment types, frequencies) stay canonical. English-only; no new
locale yet.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/components/activity/activity-view.tsx

@@ -13,6 +13,7 @@ import {
   Stethoscope,
 } from "lucide-react";
 import { useEffect, useMemo, useState } from "react";
+import { useTranslation } from "react-i18next";
 
 import { Avatar, AvatarFallback } from "@/components/ui/avatar";
 import { Card } from "@/components/ui/card";
@@ -80,6 +81,7 @@ function Kpi({
 }
 
 export function ActivityView() {
+  const { t } = useTranslation();
   const [entries, setEntries] = useState<ActivityEntry[]>([]);
 
   useEffect(() => {
@@ -108,19 +110,27 @@ export function ActivityView() {
     const today = entries.filter((e) => new Date(e.createdAt) >= startOfToday);
     const week = entries.filter((e) => new Date(e.createdAt) >= startOfWeek);
     return [
-      { label: "Changes today", value: String(today.length), icon: ActivityIcon },
-      { label: "This week", value: String(week.length), icon: CalendarDays },
-      { label: "Total recorded", value: String(entries.length), icon: Hash },
+      {
+        label: t("activity.changesToday"),
+        value: String(today.length),
+        icon: ActivityIcon,
+      },
+      { label: t("activity.thisWeek"), value: String(week.length), icon: CalendarDays },
+      {
+        label: t("activity.totalRecorded"),
+        value: String(entries.length),
+        icon: Hash,
+      },
     ];
-  }, [entries]);
+  }, [entries, t]);
 
   return (
     <div className="mx-auto flex w-full max-w-3xl flex-col gap-10 px-6 py-10">
       <div>
-        <h1 className="font-semibold text-2xl tracking-tight">Activity</h1>
-        <p className="text-muted-foreground text-sm">
-          An audit log of record changes across the clinic.
-        </p>
+        <h1 className="font-semibold text-2xl tracking-tight">
+          {t("activity.title")}
+        </h1>
+        <p className="text-muted-foreground text-sm">{t("activity.subtitle")}</p>
       </div>
 
       <div className="grid grid-cols-1 gap-4 sm:grid-cols-3">
@@ -131,8 +141,7 @@ export function ActivityView() {
 
       {entries.length === 0 ? (
         <div className="rounded-2xl border border-dashed bg-card/20 px-4 py-12 text-center text-muted-foreground text-sm">
-          No activity yet. Changes to patients, notes, appointments,
-          prescriptions and tasks will appear here.
+          {t("activity.empty")}
         </div>
       ) : (
         <ol className="flex flex-col">