fix: prevent negative CShM values and NaN RMSD display for perfect ge…

[HenriqueCSJ]

…ometries

The CShM calculation could produce slightly negative values (e.g., -0.0000) for perfect octahedral geometries due to floating-point precision errors when overlapNorm exceeded 1.0. This caused:

1. CShM displaying as "-0.0000" instead of "0.0000"
2. RMSD showing "NaN" (sqrt of negative number)

Fixes:

• Clamp overlapNorm to [-1, 1] in shapeCalculator.js to prevent overflow
• Add Math.max(0, ...) to ensure CShM is never negative
• Add safeguards in qualityMetrics.js for RMSD calculation
• Update all display components to handle edge cases with Math.max(0, ...) and Number.isFinite() checks