Extend to ternary alloy systems

[jmeyer1980]

Description

Support ternary alloys (3 elements) for more complex compositions.

Tasks

• Extend VAE to handle 3-component compositions
• Update composition constraints for ternary (5-85% per element)
• Add ternary-specific synthesis methods
• Update UI to support 3rd element selection
• Train classifier on ternary alloy data
• Validate with known ternary systems

Estimate: 6-8 hours