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/test/setup.ts

@@ -21,6 +21,12 @@ class ResizeObserver {
 
 window.ResizeObserver = ResizeObserver;
 
+// JSDOM has no layout/scrolling; Mantine Combobox scrolls the active option.
+Object.defineProperty(HTMLElement.prototype, "scrollIntoView", {
+	configurable: true,
+	value: () => {},
+});
+
 Object.defineProperty(window, "matchMedia", {
 	writable: true,
 	value: (query: string) => ({