feat(i18n): reactive Chinese (zh-CN) localization for all main panels

[skloxo]

This PR implements complete and reactive Chinese (zh-CN) localization across all major pages, and updates term definitions to align with professional financial quant terminology.

Key Changes

• Standardized terminology: Renamed "Alpha Zoo" / "Alpha 动物园" to "Alpha 因子库" (Alpha Library) and "zoos" to "因子集/分类".
• Mapped reactive translation hooks (useTranslation()) on layout links, welcome screens, agent swarm progress, validation panels, and correlation matrices.
• Added translation keys for all chart legends, search filter dropdowns, and empty states.

Verification

• Built frontend cleanly (npm run build completed with zero errors).

[warren618]

Thanks @skloxo! Merged as 4a4f3a0. The main Web UI panels — charts, chat, Alpha Library, Correlation, Run Detail — now flow through reactive English / zh-CN translations, with en.json and zh-CN.json fully aligned. 🙏