feat: add draw.rotated_rectangle primitive

[wkentaro]

Summary

• Add imgviz.draw.rotated_rectangle(image, center, size, angle, fill=None, outline=None, width=1) and its in-place pair rotated_rectangle_, for oriented bounding boxes.
• center is (cy, cx), size is (height, width) before rotation, angle is in degrees (positive rotates clockwise, since the image y-axis points down).
• Computes the four rotated corners with a rotation matrix and delegates drawing to the existing draw.polygon_, so fill/outline/width semantics and validation live in one place. Calls require_fill_or_outline at its own entry, matching the other _ primitives.
• width defaults to 1 (not 0 like rectangle/rounded_rectangle): it wraps polygon_, where PIL treats width=0 as a no-op outline, so 1 is the meaningful default here.

Test plan

• tests added: tests/unit/draw/_rotated_rectangle_test.py — axis-aligned at angle=0, extent-swap at angle=90, clockwise rotation-direction check, area preservation under rotation, outline-only path, fill+outline together, the fill/outline guard, and in-place mutation
• uv run pytest tests/unit/draw/
• uv run ruff check / uv run ruff format --check / uv run ty check clean on touched files

Closes #153