feat: enhance UI, fix backend routes, and add E2E quality gates

- UI: Polish PlanView toggles, buttons, and fix missing icons (running/activity).
- Backend: Fix route shadowing in main.py, add startup route check, and improve API test coverage.
- Tests: Add Playwright E2E smoke test, eslint-plugin-import, and integrate all into 'make check'.

frontend/e2e/smoke.spec.js

@@ -0,0 +1,38 @@
+import { test, expect } from '@playwright/test'
+
+test('smoke test - app loads and editor opens', async ({ page }) => {
+  // Mock the backend API to ensure frontend can be tested in isolation
+  await page.route('**/api/workouts', async (route) => {
+    await route.fulfill({
+      status: 200,
+      contentType: 'application/json',
+      body: JSON.stringify([])
+    })
+  })
+
+  // 1. Visit Home
+  await page.goto('/')
+
+  // 2. Verify Title
+  await expect(page).toHaveTitle(/FitMop/)
+
+  // 3. Verify Main Content
+  // Depending on default view, might need to click nav.
+  // Assuming default is Dashboard or Plans.
+  // Let's interact with the specific elements we know exist.
+  const navButton = page.getByRole('button', { name: 'Workout Plans' })
+  if (await navButton.isVisible()) {
+    await navButton.click()
+  }
+
+  await expect(page.getByRole('heading', { name: 'Workout Plans' })).toBeVisible()
+
+  // 4. Navigate to Editor
+  await page.getByRole('button', { name: 'New Plan' }).click()
+
+  // 5. Verify Editor
+  await expect(page.getByPlaceholder('Workout Name').first()).toBeVisible()
+  await expect(page.getByText('Add Step')).toBeVisible()
+
+  // 6. Check for console errors (implicit in Playwright if configured, but let's be explicit if needed)
+})