feat(seq-tools): motif categories & structure overlay, dot-plot scoring & features, cross-tool links

feat(alignment): show matched/mismatched/gaps/length stats across all alignment views via shared AlignmentStatsBar

feat(export): add downloads to ADMET, MD, pairwise, AlphaFold, docking, pathway, plus 4 new learn topics

Add global/local BLAST modes, full-length pairwise alignment view, standalone pairwise tool