Add rotation to texts (#228)

Text gains an optional `rotation` - degrees counter-clockwise about the
anchor point in graphics (y-up) space, so `rotation: 90` reads
bottom-to-top. Applied in all three renderers (SVG, canvas, PNG), each
negating into its clockwise screen space; SVG bounds account for the
rotated corners so rotated text is never clipped.

Motivation: the schematic-trace-solver's inline net labels run parallel
to the trace they name, and a vertical trace's label was being drawn
horizontally across the wire.

Co-authored-by: Claude Opus 5 <noreply@anthropic.com>