Rework the uptime page, add gauge cards, fix card with code (#3090)

.changeset/fix-card-with-code-pre.md

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+---
+"@tabler/preview": patch
+---
+
+Fixed the "Card with code" widget rendering its code as plain text instead of a `pre` block.

.changeset/system-status-panel.md

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+---
+"@tabler/preview": minor
+---
+
+Added a System status panel with 60-day uptime history bars to the Uptime preview page.

.changeset/widgets-gauge-cards.md

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+---
+"@tabler/preview": minor
+---
+
+Added ApexCharts gauge cards to the Widgets preview page.