Fix E2E test locator ambiguity and lint errors

- dashboard.spec.ts: anchor regex /^\d+\s+Proxy Hosts/ to not match
  "L4 Proxy Hosts" sidebar link
- role-access.spec.ts: use exact: true for "Proxy Hosts" link
- users.spec.ts: match any user count (/\d+ users?/) since other test
  suites create additional users
- groups.spec.ts: remove unused emptyText variable
- link-account.spec.ts: remove unused context parameter

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/e2e/users.spec.ts

@@ -17,7 +17,7 @@ test.describe('Users page', () => {
   });
 
   test('displays at least one user (the admin)', async ({ page }) => {
-    await expect(page.getByText(/1 user/)).toBeVisible({ timeout: 5000 });
+    await expect(page.getByText(/\d+ users?/)).toBeVisible({ timeout: 5000 });
   });
 
   test('search input filters users', async ({ page }) => {