Add comprehensive SVG rendering unit tests

68 tests verifying exact SVG element counts for every primitive type
in both schematic and PCB rendering. Covers lines, rectangles, ellipses,
arcs, pins, labels, wires, polylines, polygons, beziers, rounded rects,
pies, elliptical arcs, junctions, net labels, parameters, text frames,
images, power objects, tracks, pads, vias, fills, regions, text, and
component bodies. Includes edge cases for hidden elements, empty text,
transparent fills, line styles, colors, and composite components.

Author: issus