feat(plotly): implement contour-filled (#2510)

## Implementation: `contour-filled` - plotly

Implements the **plotly** version of `contour-filled`.

**File:** `plots/contour-filled/implementations/plotly.py`

---
:robot: *[impl-generate
workflow](https://github.com/MarkusNeusinger/pyplots/actions/runs/20585400365)*

---------

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

Author: github-actions[bot]

plots/contour-filled/implementations/plotly.py

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+""" pyplots.ai
+contour-filled: Filled Contour Plot
+Library: plotly 6.5.0 | Python 3.13.11
+Quality: 93/100 | Created: 2025-12-30
+"""
+
+import numpy as np
+import plotly.graph_objects as go
+
+
+# Data - Create a meshgrid with multiple Gaussian peaks for interesting contours
+np.random.seed(42)
+x = np.linspace(-3, 3, 80)
+y = np.linspace(-3, 3, 80)
+X, Y = np.meshgrid(x, y)
+
+# Create surface with multiple Gaussian peaks and a saddle point
+z1 = 2 * np.exp(-((X - 1) ** 2 + (Y - 1) ** 2))  # Peak at (1, 1)
+z2 = 1.5 * np.exp(-((X + 1) ** 2 + (Y + 1) ** 2))  # Peak at (-1, -1)
+z3 = -1 * np.exp(-((X - 1) ** 2 + (Y + 1) ** 2))  # Valley at (1, -1)
+z4 = 0.5 * np.exp(-((X + 1.5) ** 2 + (Y - 1.5) ** 2))  # Smaller peak
+Z = z1 + z2 + z3 + z4
+
+# Create filled contour plot
+fig = go.Figure()
+
+# Add filled contours
+fig.add_trace(
+    go.Contour(
+        x=x,
+        y=y,
+        z=Z,
+        colorscale="Viridis",
+        contours=dict(coloring="heatmap", showlabels=True, labelfont=dict(size=14, color="white")),
+        colorbar=dict(
+            title=dict(text="Surface Value", font=dict(size=20)), tickfont=dict(size=16), thickness=25, len=0.9
+        ),
+        ncontours=15,
+        line=dict(width=1, color="white"),
+    )
+)
+
+# Update layout for large canvas
+fig.update_layout(
+    title=dict(text="contour-filled · plotly · pyplots.ai", font=dict(size=28), x=0.5, xanchor="center"),
+    xaxis=dict(
+        title=dict(text="X Coordinate", font=dict(size=22)),
+        tickfont=dict(size=18),
+        showgrid=True,
+        gridwidth=1,
+        gridcolor="rgba(128, 128, 128, 0.3)",
+    ),
+    yaxis=dict(
+        title=dict(text="Y Coordinate", font=dict(size=22)),
+        tickfont=dict(size=18),
+        showgrid=True,
+        gridwidth=1,
+        gridcolor="rgba(128, 128, 128, 0.3)",
+        scaleanchor="x",
+        scaleratio=1,
+    ),
+    template="plotly_white",
+    margin=dict(l=100, r=120, t=100, b=100),
+)
+
+# Save as PNG and HTML
+fig.write_image("plot.png", width=1600, height=900, scale=3)
+fig.write_html("plot.html", include_plotlyjs="cdn")

plots/contour-filled/metadata/plotly.yaml

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+library: plotly
+specification_id: contour-filled
+created: '2025-12-30T00:02:58Z'
+updated: '2025-12-30T00:08:55Z'
+generated_by: claude-opus-4-5-20251101
+workflow_run: 20585400365
+issue: 0
+python_version: 3.13.11
+library_version: 6.5.0
+preview_url: https://storage.googleapis.com/pyplots-images/plots/contour-filled/plotly/plot.png
+preview_thumb: https://storage.googleapis.com/pyplots-images/plots/contour-filled/plotly/plot_thumb.png
+preview_html: https://storage.googleapis.com/pyplots-images/plots/contour-filled/plotly/plot.html
+quality_score: 93
+review:
+  strengths:
+  - Excellent use of Viridis colormap providing colorblind-safe visualization
+  - Multiple Gaussian peaks and valley demonstrate full capability of filled contours
+  - Contour labels with white text provide precise value identification
+  - Well-structured code following KISS principles
+  - Correct aspect ratio with scaleanchor maintaining square coordinate system
+  - Both PNG and HTML outputs generated as expected for Plotly
+  weaknesses:
+  - Axis labels are generic (X Coordinate, Y Coordinate) without units or more descriptive
+    context
+  - Could leverage more Plotly-specific features like custom hovertemplate to show
+    (x, y, z) values on interaction