[JS-banana]

Summary

• replace the fixed 30-day library trend chart with a scoped 会话趋势 chart
• add 7 日, 30 日, 本月, and 今年 range options with 本月 as the default
• aggregate sessions by local calendar dates and leave future days/months blank instead of treating them as zero activity
• add focused helper and component tests for range behavior and date boundaries

Validation

• pnpm --dir apps/desktop exec vitest run src/renderer/src/components/library/capture-trend-data.test.tsx src/renderer/src/components/library/CaptureTrendChart.test.tsx src/renderer/src/App.test.tsx
• pnpm desktop:test
• pnpm desktop:build