[georgianastasov]

Description

Fix upgrade-packages not updating style imports in Web Components projects.

• Enable .css, .scss, and .sass file processing using the existing rewrite logic.
• Extend existing Web Components regression tests to cover all three extensions.

Related Issue

Closes #1859

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Refactoring / code cleanup
• Build / CI configuration change

Affected Packages

• igniteui-cli (packages/cli)
• @igniteui/cli-core (packages/core)
• @igniteui/angular-templates (packages/igx-templates)
• @igniteui/angular-schematics (packages/ng-schematics)
• @igniteui/mcp-server (packages/igniteui-mcp)

Checklist

• I have tested my changes locally (npm run test)
• I have built the project successfully (npm run build)
• I have run the linter (npm run lint)
• I have added/updated tests as needed
• My changes do not introduce new warnings or errors

Additional Context

• Regression tests: 23/23 passed.
• Manually reproduced the bug before the fix and verified the fix afterward.
• Manual CLI tests passed for Angular, React, and Web Components.
• Full suite: 71 failures attributed to unrelated leftover compiled test files.

[Copilot]

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[coveralls]

coverage: 94.583% (+0.001%) from 94.582% — ganastasov/style-imports into master