e2e: make tests reusable for standalone

docs/Developer Guide/Developer Guide/Testing/End-to-end tests.md

@@ -9,7 +9,12 @@
 *   Playwright with Electron
 *   Tests some basic functionality such as creating a new document.
 
-These can be found in `apps/server-e2e` and `apps/desktop/e2e`.
+Shared E2E tests live in `packages/trilium-e2e/`. Server-specific tests are in `apps/server/e2e/`, desktop tests in `apps/desktop/e2e/`.
+
+Run E2E tests via:
+- `pnpm --filter server e2e` (server)
+- `pnpm --filter client-standalone e2e` (standalone)
+- `pnpm --filter desktop e2e` (desktop/Electron)
 
 ## First-time run