Backup page: pick an application instead of assembling a strategy by hand

The page now starts with the applications found on the cluster and on the
host, each showing what it offers. Choosing one opens a short flow:
select data and database, pick how often, pick a target, save. That
creates one strategy per selected part, so Gitea's volume and its
PostgreSQL dump become two ordinary strategies with their own history.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

frontend/e2e/app-backup.spec.ts

@@ -0,0 +1,39 @@
+import { test, expect } from '@playwright/test'
+
+test('an admin backs up Gitea data and database in one flow', async ({ page }) => {
+  await page.goto('/login')
+  await page.getByLabel('Email').fill('admin@example.com')
+  await page.getByLabel('Password').fill('admin-password-123')
+  await page.getByRole('button', { name: 'Sign in' }).click()
+  await expect(page.getByRole('heading', { name: 'Dashboard' })).toBeVisible()
+  await page.goto('/backups')
+
+  // a target is needed first
+  await page.getByRole('button', { name: 'New target' }).click()
+  const name = `NAS ${Date.now()}`
+  await page.getByLabel('Name', { exact: true }).fill(name)
+  await page.getByLabel('Host', { exact: true }).fill('nas.local')
+  await page.getByLabel('Share').fill('backups')
+  await page.getByLabel('Username', { exact: true }).fill('backup')
+  await page.getByLabel('Password', { exact: true }).fill('smb-secret')
+  await page.getByRole('button', { name: 'Save target' }).click()
+  await expect(page.getByRole('row', { name: new RegExp(name) })).toBeVisible()
+
+  // the discovered applications are shown with what they offer
+  const gitea = page.getByTestId('application-k8s:gitea/gitea')
+  await expect(gitea).toContainText('Gitea')
+  await expect(gitea).toContainText('Data + DB')
+  await expect(page.getByTestId('application-host:monitoring.service')).toContainText('Monitoring')
+
+  // Gitea → select → schedule → target → save
+  await gitea.getByRole('button', { name: 'Back up' }).click()
+  await expect(page.getByRole('dialog')).toContainText('gitea-shared-storage')
+  await page.getByLabel('Target', { exact: true }).selectOption({ label: name })
+  await page.getByRole('button', { name: 'Create backup plan' }).click()
+
+  await expect(page.getByText(/2 backup strategies created/)).toBeVisible()
+  await expect(page.getByRole('row', { name: /Gitea – Gitea volume/ })).toBeVisible()
+  await expect(page.getByRole('row', { name: /Gitea – PostgreSQL dump/ })).toContainText(
+    '0 0 3 * * *',
+  )
+})