fix: preserve tenant in participant links

Build invitation and meeting URLs from the validated tenant origin and fall back when local HTTP blocks the Clipboard API.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

frontend/src/components/actions/copyText.test.ts

@@ -0,0 +1,23 @@
+import { afterEach, expect, it, vi } from 'vitest'
+import { copyText } from './copyText'
+
+const originalExecCommand = Object.getOwnPropertyDescriptor(document, 'execCommand')
+
+afterEach(() => {
+  vi.restoreAllMocks()
+  if (originalExecCommand) {
+    Object.defineProperty(document, 'execCommand', originalExecCommand)
+  } else {
+    Reflect.deleteProperty(document, 'execCommand')
+  }
+})
+
+it('falls back to a selected textarea when the Clipboard API is unavailable', async () => {
+  const copy = vi.fn().mockReturnValue(true)
+  Object.defineProperty(document, 'execCommand', { configurable: true, value: copy })
+
+  await copyText('http://ypto.guess.local:5173/participant/token')
+
+  expect(copy).toHaveBeenCalledWith('copy')
+  expect(document.querySelector('textarea')).toBeNull()
+})