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. No algorithmic changes;
all validation results unchanged.

.last_sync

@@ -1 +1 @@
-76b7d8176fca45cf99ba0b4ac9d48de03f803d67
+28ee8790a84221451b233f7896e2a94d4b739636