Improve anatomical annotations, aliases, and topology

[napakalas]

This PR improves the anatomical accuracy and consistency of the human flatmaps by:

• Fixing incorrect and missing annotations across multiple structures.
• Updating aliases and proxy mappings for anatomical terms.
• Refining the topology and positioning of nerves, ganglia, and plexuses, particularly around the celiac ganglion complex and autonomic nervous system.
• Adding new anatomical features and markers, including nerve plexuses, spinal tracts, and segment/dorsal root ganglion indicators.
• Cleaning up SVG files and removing unused anatomical terms and properties.