feat(seaborn): implement ridgeline-basic (#541)

## Summary
Implements `ridgeline-basic` for **seaborn**.

**Parent Issue:** #539
**Base Branch:** `plot/ridgeline-basic`

## Files
- `plots/ridgeline-basic/implementations/seaborn.py`

## Preview
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Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

Author: claude[bot]

plots/ridgeline-basic/implementations/seaborn.py

@@ -0,0 +1,95 @@
+"""
+ridgeline-basic: Ridgeline Plot
+Library: seaborn
+"""
+
+import numpy as np
+import pandas as pd
+import seaborn as sns
+
+
+# Data - Monthly temperature distributions
+np.random.seed(42)
+months = [
+    "January",
+    "February",
+    "March",
+    "April",
+    "May",
+    "June",
+    "July",
+    "August",
+    "September",
+    "October",
+    "November",
+    "December",
+]
+
+# Generate realistic temperature data with seasonal pattern
+data = []
+base_temps = [2, 4, 8, 12, 17, 21, 24, 23, 19, 13, 7, 3]  # Typical temperate climate
+for i, month in enumerate(months):
+    temps = np.random.normal(base_temps[i], 3, 150)
+    for t in temps:
+        data.append({"month": month, "temperature": t})
+
+df = pd.DataFrame(data)
+df["month"] = pd.Categorical(df["month"], categories=months, ordered=True)
+
+# Color palette - gradient from cool to warm
+colors = sns.color_palette("coolwarm", n_colors=12)
+
+# Create ridgeline plot using FacetGrid
+sns.set_style("white")
+g = sns.FacetGrid(
+    df,
+    row="month",
+    hue="month",
+    aspect=12,
+    height=0.7,
+    palette=colors,
+    row_order=months[::-1],  # Reverse order so January at bottom
+    hue_order=months[::-1],
+)
+
+# Draw density plots
+g.map(sns.kdeplot, "temperature", bw_adjust=0.8, clip_on=False, fill=True, alpha=0.7, linewidth=1.5)
+
+# Add outline
+g.map(sns.kdeplot, "temperature", bw_adjust=0.8, clip_on=False, color="black", lw=1)
+
+# Add horizontal line at y=0
+g.refline(y=0, linewidth=1, linestyle="-", color="black", clip_on=False)
+
+# Styling - overlap the rows
+g.figure.subplots_adjust(hspace=-0.3)
+
+# Remove axes details
+g.set_titles("")
+g.set(yticks=[], ylabel="")
+g.despine(bottom=True, left=True)
+
+# Add month labels on the left
+for i, ax in enumerate(g.axes.flat):
+    ax.text(
+        -0.02,
+        0.1,
+        months[::-1][i],
+        fontweight="bold",
+        fontsize=14,
+        color=colors[::-1][i],
+        ha="right",
+        va="center",
+        transform=ax.transAxes,
+    )
+
+# Set x-axis label on bottom plot only
+g.axes[-1, 0].set_xlabel("Temperature (°C)", fontsize=16)
+g.axes[-1, 0].tick_params(axis="x", labelsize=12)
+
+# Title
+g.figure.suptitle("Monthly Temperature Distribution", fontsize=20, fontweight="bold", y=0.98)
+
+# Save
+g.figure.set_size_inches(16, 9)
+g.savefig("plot.png", dpi=300, bbox_inches="tight")