198: Add network file import/export support for GraphML, GEXF, XGMML, CX2, DOT, and GML

[glstott]

Adds support for network file import/export, addressing GH issue #198 . This branch adds a new GraphMLService that imports supported network document formats into MicrobeTrace nodes/links and exports the current session as GraphML.

Summary:

• Adds import support for GraphML, GEXF, XGMML, Cytoscape CX2, DOT/Graphviz, and GML files.
• Detects these files by extension/content and classifies them as Network files in the upload table.
• Preserves topology, node/link attributes, labels, weights/distances, directions, coordinates/visual metadata where supported, and graph-level provenance.
• Scopes imported edge origins by filename to avoid provenance collisions across multiple imported network files.
• Adds readable field aliases for imported metadata, while retaining raw parser fields on records.
• Adds a File menu action to export the active MicrobeTrace session as microbetrace.graphml.
• Shows a Network Import Warnings dialog for unsupported or partially supported features such as nested GraphML graphs, ports, hyperedges, GEXF dynamic/hierarchy/viz metadata, CX2 fragments/status issues, and generated endpoint nodes.
• Updates 2D link label handling so imported edge label fields can be selected and displayed without being overwritten by Cytoscape render labels.
• Improves titleize formatting for imported snake/kebab-case fields and common network-format acronyms.
• Adds Cypress fixtures and a new ingestion spec covering GraphML import/export plus GEXF, XGMML, CX2, DOT, and GML import behavior.
• Extends Cypress file helpers with network MIME types and a network file datatype.

[glstott]

I reverted the label collision changes to move to another branch, keeping this one as solely network file import/export.

[glstott]

No failed cypress tests, ready for merge.