Sync from GitHub: Refactor analyzer into mixin modules for maintainability

Split monolithic core/analyzer.py into focused mixin modules
(spectrum, envelope, scoring, isotope, charge) composed via MRO.
Deduplicate adduct parser in webapp, fix typo in index.html.
Update project structure in README. Keep only GG208.txt sample.
No algorithmic changes; all validation results unchanged.

.last_sync

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