✨ feat(frontend): Storybook + auto-generated Playwright e2e docs with screenshots (#30)

Storybook 8 + Playwright JSON reporter + auto-generated markdown docs with embedded screenshots and breadcrumbs. Frontend PRs now reviewable from Gitea web UI. ~95% Mistral autonomous via ICM workspace, trainer commit/PR (Mistral hit turn limit).

Co-authored-by: Gabriel Radureau <arcodange@gmail.com>
Co-committed-by: Gabriel Radureau <arcodange@gmail.com>

frontend/.storybook/preview.ts

@@ -0,0 +1,15 @@
+import type { Preview } from '@storybook/vue3'
+
+const preview: Preview = {
+  parameters: {
+    actions: { argTypesRegex: '^on[A-Z].*' },
+    controls: {
+      matchers: {
+        color: /(background|color)$/i,
+        date: /Date$/i,
+      },
+    },
+  },
+}
+
+export default preview