test: migrate golden tests to golden_matrix and cover all custom widgets

[Autocrab]

What this PR does

It rewrites the golden tests for the Auris custom widgets. Now the tests use the golden_matrix package, cover both light and dark themes, and include all 14 widgets.

Added

• golden_matrix: 1.1.1 as a dev dependency (pinned to the exact version, no ^).
• Golden coverage for 5 widgets that had none before: AurisDataRow, AurisNotification, AurisHexOrnament, AurisScanBracket, AurisTerminal.
• Extra states for widgets that already had tests, for example AurisPanel (accent / plain), AurisProgressBar (mid / full) and AurisStatCard (positive / negative delta).

Changed

• Goldens now live in their own folder, test/golden/goldens/, split by widget and scenario (for example aurisbadge/variants/dark_en_ltr_1x.png). This keeps them separate from the unit tests and their files.
• Every scenario is captured in both AurisTheme.dark() and AurisTheme.light(). This closes the gap where light was never tested. In total there are now 40 baseline images (20 scenarios × 2 themes).

Removed

• The old test/auris_golden_test.dart file.
• The old flat baselines in test/goldens/ (9 PNG files). They are replaced by the new folder layout.

[Autocrab]

Comment: Goldens generated on MacOS, so if you work on Ubuntu\Windows then u should regenerate them locally. AFAIK there are no golden tests checks on CI