[31b4]

Closes #177

Summary

Balance history now uses EasyUI-style area charts that follow the selected app palette. Original has blue chart surfaces and accents; Monochrome and Red Filter have native neutral and red light/dark color systems across the interface, replacing their page filters.

Changes

• Adapt the EasyUI interactive area chart with smooth bounded curves, fading fills, animated reveals, range pills and pointer/touch/keyboard inspection. Retain the MIT license and support reduced motion.
• Preserve actual date spacing, source gaps, native/reporting currencies, exact dated readouts, privacy, portfolio metadata, retry states and previous-month comparison. Show cash/account trend lines by default with a hide toggle; keep net-invested overlays optional. Cash range pills update the existing page/URL filters atomically.
• Give Monochrome neutral tokens for surfaces, text, borders, controls and primary balance curves in both display modes. Retain green/red income, expense and gain/loss cues, amber warnings, purple forecasts and distinct category/split-allocation colors. Dashboard cash-flow bars use semantic income/expense colors. Use contrasting button icons and switch thumbs, and let portalled controls inherit the palette. The existing saved Monochrome preference now selects this palette without a page filter.
• Remove chart-local palette overrides so area charts use blue in Original and white/charcoal in Monochrome. Give Red Filter deep red dark surfaces, warm pale light surfaces and red primary chart/control accents. Like Monochrome, retain green income/gains, red expenses/losses, amber warnings, purple forecasts and distinct category/split-allocation colors in both display modes. Existing saved preferences select the native palette and clear legacy filters.
• Make Settings previews reflect the display mode and each theme's own palette, with readable selection marks. Add persistence, filter-transition, preview, chart-inspection and financial-gap regression coverage.

Verification

• Node 22.23.2: all 553 client tests passed, production build passed, client lint passed with zero warnings, and git diff checks passed.
• Browser verified dark/light Monochrome, Original and native Red Filter, 1280px desktop and 390px phone layouts, privacy and the transaction editor without saving. Computed styles confirmed filter-free native palettes, neutral/red chart colors, and blue Original chart colors. Red Filter persists after reload. Verified semantic chart/category/Money Map colors in dark Monochrome, readable light-mode investment returns on phones, and Red Filter semantic colors on desktop charts and light mobile dashboard cash-flow bars; unknown or stale holding trends remain neutral.
• Preview uses an isolated local D1 copy of the supplied export, upgraded through existing migrations with a clean foreign-key check. The import, local configurations and private financial data remain outside the PR; no production resources were changed.