feat: add all-accounts portfolio pages

Reuse account sections and group securities with per-account holdings.

Use Mantine Select to preserve filters and reset pagination on scope changes.

Document component reuse guardrails and cover routes, grouping and scope switching.

src/app/ui/AppBreadcrumbs.tsx

@@ -1,7 +1,9 @@
+import { Stack } from "@mantine/core";
 import type { FC } from "react";
 import { useTranslation } from "react-i18next";
 import { useMatch } from "react-router";
 import { AccountBreadcrumbs } from "./AccountBreadcrumbs";
+import { AccountScopeSwitch } from "./AccountScopeSwitch";
 import { BreadcrumbTrail } from "./BreadcrumbTrail";
 
 const AppBreadcrumbs: FC = () => {
@@ -18,27 +20,50 @@ const AppBreadcrumbs: FC = () => {
 
 	if (operations)
 		return (
-			<AccountBreadcrumbs
-				accountId={operations.params.accountId ?? ""}
-				section="operations"
-			/>
+			<Stack gap="sm" mb="lg">
+				<AccountBreadcrumbs
+					accountId={operations.params.accountId ?? ""}
+					section="operations"
+				/>
+				<AccountScopeSwitch
+					accountId={operations.params.accountId ?? ""}
+					section="operations"
+				/>
+			</Stack>
 		);
 	if (events)
 		return (
-			<AccountBreadcrumbs
-				accountId={events.params.accountId ?? ""}
-				section="events"
-			/>
+			<Stack gap="sm" mb="lg">
+				<AccountBreadcrumbs
+					accountId={events.params.accountId ?? ""}
+					section="events"
+				/>
+				<AccountScopeSwitch
+					accountId={events.params.accountId ?? ""}
+					section="events"
+				/>
+			</Stack>
 		);
 	if (income)
 		return (
-			<AccountBreadcrumbs
-				accountId={income.params.accountId ?? ""}
-				section="income"
-			/>
+			<Stack gap="sm" mb="lg">
+				<AccountBreadcrumbs
+					accountId={income.params.accountId ?? ""}
+					section="income"
+				/>
+				<AccountScopeSwitch
+					accountId={income.params.accountId ?? ""}
+					section="income"
+				/>
+			</Stack>
 		);
 	if (account)
-		return <AccountBreadcrumbs accountId={account.params.accountId ?? ""} />;
+		return (
+			<Stack gap="sm" mb="lg">
+				<AccountBreadcrumbs accountId={account.params.accountId ?? ""} />
+				<AccountScopeSwitch accountId={account.params.accountId ?? ""} />
+			</Stack>
+		);
 	if (accounts)
 		return <BreadcrumbTrail items={[{ label: t("breadcrumbs.accounts") }]} />;
 	if (settings)