feat(highcharts): implement line-basic (#478)

## Summary
Implements `line-basic` for **highcharts** library.

**Parent Issue:** #205
**Sub-Issue:** #455
**Base Branch:** `plot/line-basic`
**Attempt:** 1/3

## Implementation
- `plots/highcharts/line/line-basic/default.py`

## Changes
- Fixed import path for LineSeries (from
`highcharts_core.options.series.area`)
- Set correct window size for 4800x2700 screenshot
- Clean KISS-style implementation following plot-generator guidelines

Co-authored-by: claude[bot] <41898282+claude[bot]@users.noreply.github.com>

Author: claude[bot]

plots/highcharts/line/line-basic/default.py

@@ -92,7 +92,7 @@
 chrome_options.add_argument("--no-sandbox")
 chrome_options.add_argument("--disable-dev-shm-usage")
 chrome_options.add_argument("--disable-gpu")
-chrome_options.add_argument("--window-size=4900,2800")
+chrome_options.add_argument("--window-size=4800,2700")
 
 driver = webdriver.Chrome(options=chrome_options)
 driver.get(f"file://{temp_path}")