refactor: Move `ui.Theme.from_brand()` Sass code into an `.scss` file #6027

Job	Run time
check (3.12, ubuntu-latest)	2m 52s
check (3.12, windows-latest)	6m 12s
check (3.12, macOS-latest)	3m 12s
check (3.11, ubuntu-latest)	2m 38s
check (3.11, windows-latest)	6m 28s
check (3.11, macOS-latest)	1m 59s
check (3.10, ubuntu-latest)	2m 51s
playwright-deploys-precheck (3.10)	1m 26s
check (3.10, windows-latest)	5m 21s
check (3.10, macOS-latest)	2m 40s
check (3.9, ubuntu-latest)	2m 37s
check (3.9, windows-latest)	6m 29s
check (3.9, macOS-latest)	2m 20s
playwright-examples (3.12, chromium)	3m 43s
test-narwhals-integration	3m 59s
playwright-examples (3.12, firefox)	4m 22s
playwright-examples (3.12, webkit)	3m 58s
playwright-examples (3.11, chromium)	4m 12s
playwright-examples (3.11, firefox)	4m 25s
playwright-shiny (3.12, chromium)	5m 7s
playwright-examples (3.11, webkit)	3m 57s
playwright-shiny (3.12, firefox)	5m 2s
playwright-examples (3.10, chromium)	3m 38s
playwright-shiny (3.12, webkit)	5m 0s
playwright-examples (3.10, firefox)	4m 14s
playwright-shiny (3.11, chromium)	4m 30s
playwright-examples (3.10, webkit)	4m 9s
playwright-shiny (3.11, firefox)	5m 16s
playwright-examples (3.9, chromium)	3m 41s
playwright-shiny (3.11, webkit)	4m 48s
playwright-examples (3.9, firefox)	4m 5s
playwright-shiny (3.10, chromium)	4m 21s
playwright-examples (3.9, webkit)	4m 12s
playwright-shiny (3.10, firefox)	5m 31s
playwright-shiny (3.10, webkit)	4m 29s
playwright-shiny (3.9, chromium)	4m 23s
playwright-shiny (3.9, firefox)	4m 58s
Deploy to PyPI	0s
	2h 33m 5s

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