PAP-1627: route sidebar memories link through active company prefix

The sidebar's Memories link was resolving to `/memories` instead of
`/:companyPrefix/memories` because `memories` was not in
`BOARD_ROUTE_ROOTS`. Without it, `applyCompanyPrefix` treated the path
as if `memories` were already a company prefix and skipped rewriting.

- Add `memories` to `BOARD_ROUTE_ROOTS` so `applyCompanyPrefix("/memories", "PAP")` returns `/PAP/memories`.
- Add a regression test covering `/memories` through `isBoardPathWithoutPrefix`, `extractCompanyPrefixFromPath`, and `applyCompanyPrefix`.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

ui/src/lib/company-routes.test.ts

@@ -20,4 +20,10 @@ describe("company routes", () => {
       "/execution-workspaces/workspace-123",
     );
   });
+
+  it("treats memories as a company board route", () => {
+    expect(isBoardPathWithoutPrefix("/memories")).toBe(true);
+    expect(extractCompanyPrefixFromPath("/memories")).toBeNull();
+    expect(applyCompanyPrefix("/memories", "PAP")).toBe("/PAP/memories");
+  });
 });

ui/src/lib/company-routes.ts

@@ -9,6 +9,7 @@ const BOARD_ROUTE_ROOTS = new Set([
   "workspaces",
   "execution-workspaces",
   "issues",
+  "memories",
   "routines",
   "goals",
   "approvals",