Add dashexamplechartjs module for the new Symfony dashboard hooks

[nicosomb]

Description

PoC for spike PrestaShop/PrestaShop#41970 (chart library benchmark) — validates Chart.js as the replacement for D3 v3 + NVD3 on the migrated (Symfony) Back Office Dashboard, using the same integration contract as the reference dashexample module from PrestaShop/PrestaShop#41968 / #254.

What it demonstrates

• Registers on the new dashboard hooks: displayAdminDashboardZoneOne, displayAdminDashboardZoneTwo, displayAdminDashboardToolbar. No legacy Smarty/HelperForm/Db::getInstance().
• Renders hook content through module Twig templates ($this->get('twig')), self-hosts Chart.js v4.5.1 (MIT, no CDN dependency).
• Covers the 4 chart types the current native widgets need: doughnut (dashactivity equivalent), line/area with a previous-period overlay (dashtrends equivalent), bar (dashgoals equivalent).
• Sample/static data only — this is a rendering/integration PoC, not a full reimplementation of the native widgets' data layer.

Requirements

• PrestaShop 9.2.0+, with core PR PrestaShop/PrestaShop#42077 merged.
• The dashboard feature flag enabled.

Known issues on the dependency (PrestaShop/PrestaShop#42077)

Building this PoC surfaced two bugs in the core PR this module depends on (reported there):

• index.html.twig is missing |raw on toolbarContent/topContent, breaking the toolbar-based asset-loading pattern this module (and dashexample) rely on.
• The date-range calendar form loses its security token on submit (GET form whose action already contains ?_token=..., dropped and rebuilt from form fields alone), redirecting to security/compromised.

Chart.js benchmark

Chart.js was selected as the primary recommendation among Chart.js / ApexCharts / Billboard.js: MIT license, ~67.5k★ on GitHub, ~54M downloads/month, ~68 KB gzip, no license risk — over ApexCharts (excluded: proprietary relicensing in June 2025, revenue-gated + no-redistribution clause) and Billboard.js (heavier bundle, smaller community, keeps a D3 v7 dependency).

Known gap surfaced by this PoC: Chart.js renders on <canvas>, invisible to screen readers by default. This PoC adds role="img" + aria-label as a minimal baseline; a real migration should budget explicit accessibility work per chart.

How to test

1. On a 9.2.0+ shop with PR #42077 merged, enable the dashboard feature flag.
2. Install the module: php bin/console prestashop:module install dashexamplechartjs.
3. Open the Dashboard: doughnut/line/bar charts render in Zone One / Zone Two.

Draft PR — opening for early visibility/discussion while PrestaShop/PrestaShop#42077 is still open.

[nicosomb]