## Context

The candlestick chart is rendered using the lightweight-charts library in `CandleChart.tsx`. Currently, the chart uses green (`#10b981`) for up candles and red (`#ef4444`) for down candles, with matching wick colors. This change updates the color scheme to a classic black/white pattern.

The lightweight-charts library configures candlestick colors through the `addCandlestickSeries` options, specifically:
- `upColor`: Interior fill color for bullish candles
- `downColor`: Interior fill color for bearish candles
- `wickUpColor`: Wick color for bullish candles
- `wickDownColor`: Wick color for bearish candles
- `borderUpColor`: Border color for bullish candles
- `borderDownColor`: Border color for bearish candles
- `borderVisible`: Whether to show borders

## Goals / Non-Goals

**Goals:**
- Update up candles to white interior with black outline
- Update down candles to solid black
- Maintain visual clarity and readability of the chart

**Non-Goals:**
- Adding user-configurable color themes
- Changing annotation or marker colors
- Modifying any chart behavior beyond visual appearance

## Decisions

### Decision 1: Color Values
- **Up candles**: `upColor: '#ffffff'`, `borderUpColor: '#000000'`, `wickUpColor: '#000000'`, `borderVisible: true`
- **Down candles**: `downColor: '#000000'`, , `borderDownColor: '#000000'`, `wickDownColor: '#000000'`

**Rationale**: Pure white (`#ffffff`) and pure black (`#000000`) provide maximum contrast and match traditional financial charting conventions. Borders must be visible for up candles to show the black outline.

**Alternatives considered**:
- Using slightly off-white or gray tones: Rejected as it reduces clarity
- Making borders visible for both up and down candles: Unnecessary for down candles since they're solid black

### Decision 2: Implementation Location
Update the `addCandlestickSeries` configuration in the chart initialization effect in `CandleChart.tsx`.

**Rationale**: This is the single location where candlestick series styling is configured.

**Alternatives considered**:
- Creating a separate color configuration object: Overkill for a simple color change
- Using CSS or theme variables: Not supported by lightweight-charts API for series colors

## Risks / Trade-offs

**[Risk]** White candles may have reduced visibility on light backgrounds → **Mitigation**: Black borders ensure visibility; background color is already `#ffffff`

**[Trade-off]** Deviating from common green/red convention → **Benefit**: More professional appearance and better for users with color vision deficiencies
