feat(search): Add PyPI package search

[vredchenko]

Summary

Add a filter chip to search PyPI packages relevant to the smartem ecosystem.

Scope

Curated list of packages:

• smartem-decisions
• smartem-agent
• smartem-common
• (other relevant packages)

Data Sources

• Package Index JSON API
• Warehouse API
• Web scraping (fallback)

Implementation Approaches

1. Simple: Search within specific configured packages
2. Complex: Broader package discovery

Files to Modify

• core/webui-config.ts (package list)
• webui/src/types/search.ts (add type)
• webui/src/hooks/useSearch.ts (search logic)
• webui/src/components/widgets/SearchPalette/SearchPalette.tsx

Priority

Future enhancement - optional for initial release.

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From PR #124 review comment (Item 9)