docs: expand Circuit Diagram Builder technical guide

[dragosandreibobu]

What changed

• Replaced the brief README with a complete user and technical guide.
• Added a custom workflow SVG and Mermaid architecture diagrams.
• Documented component placement, rotation, connection, movement and zoom controls.
• Explained the .PS symbol-definition model, Code::Blocks/WinBGIm build path and Windows-specific constraints.
• Corrected the earlier implication that ordinary Linux GCC could build the application unchanged.
• Added honest limits around simulation, fixed arrays, routing and repository hygiene.

Validation

The README was cross-checked against Electron.cbp, Electron/unitedCode.cpp, the included component-definition files and the committed Windows executable path.