Explain the hybrid technology pipeline

[Jayktopus]

What changed

• adds an English and German Technology explained page
• provides a plain-language overview and a detailed, code-aligned pipeline description
• documents calibration, OpenCV, SAM, Light HQ-SAM, fusion scoring, material-edge refinement, CAD fitting, uncertainty, fallbacks and FreeCAD export gates
• adds a Mermaid architecture diagram and an implementation map
• links each language version from the primary README navigation

Why

Users and contributors should be able to understand what the hybrid does, which parts are measured, where learned models are used, and where Scan2Sketch deliberately refuses to claim certainty.

Validation

• 198 tests pass
• all local Markdown links resolve
• Mermaid and code fences are balanced
• git diff --check passes