feat: roll out illustrative empty states across 8 pages with 2 new guide entries

- TreeLibraryPage: split empty state into no-flows (illustration + CTA) vs no-filter-results
- MyAnalyticsPage/TeamAnalyticsPage: add zero-sessions empty state with illustration
- SessionHistoryPage: split into no-sessions (illustration) vs no-filter-results
- StepLibraryBrowser: illustrative empty state when no steps exist
- ScriptTemplateList: replace plain empty state with ScriptIllustration
- MySharesPage: replace icon-based empty state with ShareIllustration
- IntegrationsPage: add IntegrationIllustration above setup form
- Add script-templates and psa-setup guides to guides data
- Add EmptyState vitest tests (7 tests)

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

frontend/src/components/common/__tests__/EmptyState.test.tsx

@@ -0,0 +1,92 @@
+import { describe, it, expect } from 'vitest'
+import { render, screen } from '@testing-library/react'
+import { BrowserRouter } from 'react-router-dom'
+import { EmptyState } from '../EmptyState'
+import { FlowIllustration } from '../EmptyStateIllustrations'
+
+function renderWithRouter(ui: React.ReactElement) {
+  return render(<BrowserRouter>{ui}</BrowserRouter>)
+}
+
+describe('EmptyState', () => {
+  it('renders title and description', () => {
+    renderWithRouter(
+      <EmptyState
+        title="No items found"
+        description="Try adjusting your filters."
+      />
+    )
+
+    expect(screen.getByText('No items found')).toBeInTheDocument()
+    expect(screen.getByText('Try adjusting your filters.')).toBeInTheDocument()
+  })
+
+  it('renders illustration when provided', () => {
+    const { container } = renderWithRouter(
+      <EmptyState
+        title="Empty"
+        illustration={<FlowIllustration />}
+      />
+    )
+
+    const svg = container.querySelector('svg')
+    expect(svg).toBeInTheDocument()
+  })
+
+  it('renders action button', () => {
+    renderWithRouter(
+      <EmptyState
+        title="No data"
+        action={<button>Create New</button>}
+      />
+    )
+
+    expect(screen.getByRole('button', { name: 'Create New' })).toBeInTheDocument()
+  })
+
+  it('renders learn more link with correct href', () => {
+    renderWithRouter(
+      <EmptyState
+        title="Get started"
+        learnMoreLink="/guides/creating-flows"
+      />
+    )
+
+    const link = screen.getByText(/Learn more/i)
+    expect(link).toBeInTheDocument()
+    expect(link).toHaveAttribute('href', '/guides/creating-flows')
+  })
+
+  it('renders custom learn more text', () => {
+    renderWithRouter(
+      <EmptyState
+        title="Get started"
+        learnMoreLink="/guides/test"
+        learnMoreText="View guide"
+      />
+    )
+
+    expect(screen.getByText(/View guide/i)).toBeInTheDocument()
+  })
+
+  it('renders without optional props', () => {
+    renderWithRouter(<EmptyState title="Just a title" />)
+
+    expect(screen.getByText('Just a title')).toBeInTheDocument()
+    expect(screen.queryByRole('button')).not.toBeInTheDocument()
+    expect(screen.queryByRole('link')).not.toBeInTheDocument()
+  })
+
+  it('prefers illustration over icon when both provided', () => {
+    const { container } = renderWithRouter(
+      <EmptyState
+        title="Test"
+        icon={<span data-testid="icon">icon</span>}
+        illustration={<FlowIllustration />}
+      />
+    )
+
+    expect(container.querySelector('svg')).toBeInTheDocument()
+    expect(screen.queryByTestId('icon')).not.toBeInTheDocument()
+  })
+})