Nutritional Pharmacology and Mechanistic Insights of L-Arginine: Endothelial–Neuroendocrine–Reproductive Axis in the Management of Erectile Dysfunction and Related Male Disorders Mechanistic Pathways Linking Nitric Oxide Bioavailability, Hormonal Regulation, and Mitochondrial–Reproductive Restoration 0009-0007-5798-1996 DOI: 10.5281/zenodo.17569104