test: comprehensive validation & fuzz testing with bug fixes

Fix KEGG search: use find/hsa with symbol matching + parse get/PATHWAY section

Add Reactome diagrams, KEGG search, pathway enrichment (pipeline + standalone)

Fix Reactome pathway search: correct param name and response parsing

Fix Phase 1 endpoints: resolve UniProt→PDB in structure viewer, use proper Reactome search, surface real backend errors in frontend

Sprint 3-7: Alignment, Structure Viewer, Pathway Analysis, Utility Tools, analyze page fully live