feat(profiles): switch profile from the account menu

Switching was reachable only from Settings, which is the wrong place for
it: on a shared device changing who is watching is a frequent, front-door
action, not a configuration change buried three screens deep.

It sits directly under the identity block rather than among the
destinations (Downloads/Settings/Display), because it answers "who is
this?" and not "where do I go?". Shown even with one account, since the
picker is also where a second is added -- gating it on a second profile
existing would leave no way in from here.

The picker also gains a Back affordance when a session is already live.
Reaching it from the menu and changing your mind -- or failing a PIN on
someone else's tile -- previously had no way back to the session you
still had. At startup there is nothing behind it, so it stays hidden.

src/lib/components/account/AccountMenu.test.ts

@@ -73,7 +73,22 @@ describe("AccountMenu", () => {
     render(AccountMenu);
     openMenu();
     const items = screen.getAllByRole("menuitem").map((el) => el.textContent?.trim());
-    expect(items).toEqual(["Downloads", "Settings", "Display", "Sign out"]);
+    expect(items).toEqual(["Switch profile", "Downloads", "Settings", "Display", "Sign out"]);
+  });
+
+  /**
+   * "Switch profile" sits directly under the identity block, before the
+   * destinations. It answers "who is this?", not "where do I go?", and burying
+   * it in Settings is what this entry exists to undo.
+   *
+   * TRACES: UR-082 | DR-276
+   */
+  it("puts Switch profile first, next to the identity block", async () => {
+    render(AccountMenu);
+    openMenu();
+    const items = screen.getAllByRole("menuitem");
+    expect(items[0].textContent?.trim()).toBe("Switch profile");
+    expect(items[0].getAttribute("href")).toBe("/profiles");
   });
 
   it("shows the identity block with name and server host", async () => {