feat(bokeh): implement histogram-basic (#309)

## Summary
Implements `histogram-basic` for **bokeh** library.

**Parent Issue:** #206
**Sub-Issue:** #228
**Base Branch:** `plot/histogram-basic`
**Attempt:** 3/3

## Implementation
- `plots/bokeh/quad/histogram-basic/default.py`

## Changes
1. Basic histogram implementation using bokeh's `quad` glyph
2. Uses numpy to compute histogram bins (30 bins for good visual
distribution)
3. Follows style guide with 4800x2700 px output dimensions

## Dependencies
- `selenium>=4.15.0` and `webdriver-manager>=4.0.0` are already in
`lib-bokeh` dependencies in `pyproject.toml` (required for `export_png`)

## CI Notes
**Important:** The CI workflow needs to be updated to set up Chrome for
bokeh PNG export (similar to highcharts).

The fix is to update `.github/workflows/ci-plottest.yml`:
```yaml
- name: Setup Chrome for Highcharts/Bokeh
  if: steps.detect_libs.outputs.has_plots == 'true' && (contains(steps.detect_libs.outputs.libraries, 'highcharts') || contains(steps.detect_libs.outputs.libraries, 'bokeh'))
  uses: browser-actions/setup-chrome@v1
  with:
    chrome-version: stable
```

## Verified Locally
- Implementation tested locally and generates correct plot.png
(4800x2700 px)
- Code passes ruff format and lint checks

---------

Co-authored-by: claude[bot] <41898282+claude[bot]@users.noreply.github.com>
Co-authored-by: Markus Neusinger <2921697+MarkusNeusinger@users.noreply.github.com>

Author: 3 people

plots/bokeh/quad/histogram-basic/default.py

@@ -0,0 +1,51 @@
+"""
+histogram-basic: Basic Histogram
+Library: bokeh
+"""
+
+import numpy as np
+from bokeh.io import export_png
+from bokeh.plotting import figure
+
+
+# Data - 500 normally distributed values (mean=100, std=15)
+np.random.seed(42)
+values = np.random.normal(100, 15, 500)
+
+# Compute histogram bins
+hist, edges = np.histogram(values, bins=30)
+
+# Create figure (4800 x 2700 px for high resolution)
+p = figure(width=4800, height=2700, title="Basic Histogram", x_axis_label="Value", y_axis_label="Frequency")
+
+# Draw histogram using quad glyph
+p.quad(
+    top=hist,
+    bottom=0,
+    left=edges[:-1],
+    right=edges[1:],
+    fill_color="#306998",
+    fill_alpha=0.7,
+    line_color="white",
+    line_width=1,
+)
+
+# Style title
+p.title.text_font_size = "20pt"
+p.title.align = "center"
+
+# Style axis labels
+p.xaxis.axis_label_text_font_size = "20pt"
+p.yaxis.axis_label_text_font_size = "20pt"
+p.xaxis.major_label_text_font_size = "16pt"
+p.yaxis.major_label_text_font_size = "16pt"
+
+# Style grid - subtle
+p.xgrid.grid_line_alpha = 0.3
+p.ygrid.grid_line_alpha = 0.3
+
+# Ensure y-axis starts at zero
+p.y_range.start = 0
+
+# Save output
+export_png(p, filename="plot.png")