Add Chart.js charts to the dashexample module

[nicosomb]

Description

Adds Chart.js charts to the existing dashexample module (merged in #254) instead of shipping a second demo module: the earlier dashexamplechartjs PoC validated Chart.js for spike PrestaShop/PrestaShop#41970, and its learnings are now folded into the single reference module for the migrated (Symfony) Back Office Dashboard (PrestaShop/PrestaShop#41968 / #254).

The module ships no charting library: it consumes the Chart.js bundle provided by the core dashboard page (global Chart + the psChart PrestaShop palette) from PrestaShop/PrestaShop#42135.

What it demonstrates

• Four chart types across the three zones, covering the needs of the current native widgets:
  • Zone One — traffic-sources doughnut, no colors set: the core palette plugin colors it automatically (dashactivity equivalent);
  • Zone Two — sales-trend line with a previous-period overlay + goals-vs-actual bar, both picking explicit tokens from psChart.colors (dashtrends / dashgoals equivalents);
  • Zone Three — orders-by-status polar area, auto-colored per data point like the doughnut.
• The two complementary color modes of the core bundle: zero-config auto-coloring vs explicit psChart tokens (a chart that defines any color is left untouched by the auto-coloring).
• Blocks presented as Bootstrap cards (card / card-header / card-body / card-footer), the supported markup of the new BO theme.
• Per-hook asset independence: each hook template loads exactly the assets its own blocks need, so every hook keeps working when the others are unregistered.
• Hook parameters (date_from / date_to) surfaced in each card footer.
• Sample/static data only — rendering/integration reference, not a reimplementation of the native widgets' data layer.

Requirements

• PrestaShop 9.2.0+ with core PR PrestaShop/PrestaShop#42135 (Chart.js bundle + palette).
• The dashboard feature flag enabled.

Chart.js benchmark (from the spike)

Chart.js was selected among Chart.js / ApexCharts / Billboard.js: MIT license, ~67.5k★, ~54M downloads/month, ~68 KB gzip — over ApexCharts (proprietary relicensing in June 2025) and Billboard.js (heavier, keeps a D3 v7 dependency). Chart.js renders on <canvas>, invisible to screen readers by default: every canvas here carries role="img" + aria-label as a minimal baseline.

How to test

1. On a 9.2.0+ shop with Add Chart.js as an independent core bundle with a PrestaShop palette for the Symfony dashboard PrestaShop#42135, enable the dashboard feature flag.
2. Install the module: php bin/console prestashop:module install dashexample.
3. Open the Dashboard: doughnut / line / bar / polar-area charts render as cards in the three zones, colored with the PrestaShop palette; the toolbar shows the module marker and the top/bottom zones their banners.

[nicosomb]