Fix Dash template rendering and minHeight row stretch

[jeffgallini]

Summary

Debugged usage.py and fixed package issues that left some DataTable functionality broken or blank.

Root cause

Dash was hydrating column render / editor / footer templates (and loader / empty-state / sort-icon slots) via _children_props. Those wrappers cannot be safely cloned for per-row {token} interpolation, which produced:

• blank cells when the first column had a Dash component render
• console floods of Error: undefined was not found.

Fixes

• Keep template slots as dry JSON and let DataTable materialize them (same pattern as the column-filter hotfix)
• Serialize top-level Component slot props to dry dicts in the Python wrapper so the API still accepts DMC/HTML components
• Harden React template cloning for any already-hydrated Dash wrappers
• Apply minHeight on the outer wrapper instead of Mantine DataTable so sparse tables no longer stretch body rows (GitHub issue how to fix row height if the table is set minHeight #8)

Files

• dash_mantine_datatable/__init__.py
• src/lib/components/DataTable.react.js
• src/lib/styles/layers.css
• dash_mantine_datatable/dash_mantine_datatable.min.js (+ map)
• tests/test_fluent_api.py

Verification

• Unit tests: 26 passed
• Isolated Playwright repros: dmc.Text("{name}") render, ActionIcon templates, customLoader, and minHeight row height all pass with 0 undefined was not found errors
• Full usage.py app: 0 console errors; demos render (sparklines, badges, action icons, filters, loaders)