feat(pages): browse all packages without search

[tifycloud]

Summary

• show package catalogs immediately without requiring a search term
• keep browser performance bounded with 100-item pagination across all 10k+ packages
• label curated bundles and packages with explicit purpose text
• clear stale package shards synchronously when target/flavor changes
• extend Pages UI regression coverage for pagination and target switching

Verification

• ./tests/test_static.sh
• node tests/test_pages_ui.js
• python3 tests/test_component_catalog.py
• python3 tests/test_component_catalog_staging.py
• python3 tests/test_package_catalog.py
• bash tests/test_pages_policy.sh
• independent reviewer: no remaining P0/P1/P2 blockers