feat(utils): add shared styling and color palette

src/utils/styling.py

@@ -0,0 +1,127 @@
+"""Shared styling utilities and color palette for all charts."""
+
+from typing import Optional
+
+import matplotlib.figure
+import matplotlib.axes
+import matplotlib.pyplot as plt
+
+
+# ---------------------------------------------------------------------------
+# Export & sizing constants
+# ---------------------------------------------------------------------------
+
+EXPORT_DPI = 300
+FIGURE_SIZE_DEFAULT = (12, 7)  # width, height in inches
+FIGURE_SIZE_SQUARE = (8, 8)
+FIGURE_SIZE_WIDE = (16, 10)
+
+
+# ---------------------------------------------------------------------------
+# Zone colors (risk / status shading)
+# ---------------------------------------------------------------------------
+
+BUBBLE_ZONE = "#e74c3c"      # Red — danger/bubble
+WARNING_ZONE = "#f39c12"     # Orange — warning
+NORMAL_ZONE = "#27ae60"       # Green — normal/healthy
+
+
+# ---------------------------------------------------------------------------
+# Data series colors
+# ---------------------------------------------------------------------------
+
+AI_SPEND = "#2980b9"          # Blue — AI spending
+REVENUE = "#27ae60"            # Green — revenue
+AGENT_GROWTH = "#8e44ad"      # Purple — agent adoption
+DEBT = "#c0392b"               # Dark red — debt
+PRODUCTIVITY = "#16a085"       # Teal — productivity metrics
+
+
+# ---------------------------------------------------------------------------
+# Neutral colors
+# ---------------------------------------------------------------------------
+
+GRAY_LIGHT = "#ecf0f1"
+GRAY_MEDIUM = "#95a5a6"
+GRAY_DARK = "#2c3e50"
+BLACK = "#1a1a2e"
+WHITE = "#ffffff"
+
+
+# ---------------------------------------------------------------------------
+# Theme
+# ---------------------------------------------------------------------------
+
+def get_theme() -> dict:
+    """Return a matplotlib rcParams dict with a clean, professional look."""
+    return {
+        "font.family": "DejaVu Sans",
+        "font.size": 12,
+        "figure.facecolor": WHITE,
+        "figure.dpi": EXPORT_DPI,
+        "axes.facecolor": "#fafafa",
+        "axes.edgecolor": "#dddddd",
+        "axes.grid": True,
+        "axes.axisbelow": True,
+        "grid.color": "#e0e0e0",
+        "grid.linestyle": "-",
+        "grid.linewidth": 0.5,
+        "grid.alpha": 0.7,
+        "xtick.labelsize": 10,
+        "ytick.labelsize": 10,
+        "axes.titlesize": 16,
+        "axes.titleweight": "bold",
+        "axes.labelsize": 12,
+        "legend.fontsize": 9,
+        "figure.titlesize": 16,
+        "figure.titleweight": "bold",
+        "savefig.dpi": EXPORT_DPI,
+        "savefig.facecolor": WHITE,
+        "savefig.bbox": "tight",
+    }
+
+
+# ---------------------------------------------------------------------------
+# Helpers
+# ---------------------------------------------------------------------------
+
+def apply_theme(fig: matplotlib.figure.Figure, ax: Optional[matplotlib.axes.Axes] = None) -> None:
+    """Apply the professional theme to a figure and optionally its axes.
+
+    Parameters
+    ----------
+    fig : matplotlib Figure
+        The figure to theme.
+    ax : matplotlib Axes, optional
+        If provided, spine cleanup is applied to this specific axes.
+        If *None*, every axes in the figure is cleaned.
+    """
+    plt.rcParams.update(get_theme())
+    fig.set_facecolor(WHITE)
+
+    targets = [ax] if ax is not None else fig.axes
+    for axes in targets:
+        axes.set_facecolor("#fafafa")
+        axes.spines["top"].set_visible(False)
+        axes.spines["right"].set_visible(False)
+        axes.spines["left"].set_color("#cccccc")
+        axes.spines["bottom"].set_color("#cccccc")
+
+
+def get_bubble_zone_colors() -> dict:
+    """Return zone colours suitable for shaded risk regions."""
+    return {
+        "bubble": BUBBLE_ZONE,
+        "warning": WARNING_ZONE,
+        "normal": NORMAL_ZONE,
+    }
+
+
+def get_company_colors() -> dict:
+    """Return consistent brand-colour mapping for hyperscalers."""
+    return {
+        "Microsoft": "#00a4ef",
+        "Alphabet": "#4285f4",
+        "Meta": "#1877f2",
+        "Amazon": "#ff9900",
+    }