Add missing L3VNC CATMAID hosted page

The VFB app Tools > CATMAID > Hosted EM Data > Larval menu lists
L3VNC but no corresponding documentation page existed. This adds
the hosted page for the 3rd instar larval VNC EM dataset
(Gerhard et al. 2017) at l3vnc.catmaid.virtualflybrain.org.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: Robbie1977

content/en/hosted/l3vnc-catmaid.md

@@ -0,0 +1,56 @@
+---
+title: L3VNC CATMAID Data Viewer
+description: "This CATMAID (Collaborative Annotation Toolkit for Massive Amounts of Image Data) instance hosts neuroanatomical data from the Drosophila third instar larva ventral nerve cord (L3 VNC) electron microscopy dataset."
+---
+
+## Access
+
+The L3VNC CATMAID instance is hosted and maintained by Virtual Fly Brain (VFB) as part of their mission to integrate and preserve key Drosophila neuroscience datasets. The instance is accessible at:
+[https://l3vnc.catmaid.virtualflybrain.org/](https://l3vnc.catmaid.virtualflybrain.org/?pid=2&zp=0&yp=53578.49999999999&xp=71242.5&tool=tracingtool&sid0=2&s0=6&help=true&layout=h(XY,%20%7B%20type:%20%22neuron-search%22,%20id:%20%22neuron-search-1%22,%20options:%20%7B%22annotation-name%22:%20%22papers%22%7D%7D,%200.6))
+
+This resource provides access to the L3 VNC dataset and its associated neural reconstructions. Virtual Fly Brain ensures its long-term availability to the research community.
+
+## Source Publication
+
+### Contributing Publications
+- Gerhard S, Andrade I, Fetter RD, Cardona A, Schneider-Mizell CM (2017) Conserved neural circuit structure across Drosophila larval development revealed by comparative connectomics. eLife, 6:e29089. https://doi.org/10.7554/eLife.29089
+
+## Dataset Contents
+
+The viewer provides access to:
+- Serial section electron microscopy volume of a Drosophila third instar larva ventral nerve cord
+- Manually traced neuron reconstructions
+- Synaptic connectivity information
+- Associated metadata and annotations
+
+## Features
+
+This CATMAID instance enables:
+- Browser-based visualization of the serial section electron microscopy data
+- Navigation through image stacks
+- Viewing of neuron reconstructions
+- Analysis of synaptic connectivity
+- Data export functionality
+
+### Available Tools
+- Tracing tool for examining reconstructions
+- Neuron search interface with paper-based filtering
+- Connectivity analysis tools
+- Skeleton visualization options
+- API access for programmatic data retrieval (documentation: https://catmaid.readthedocs.io/en/stable/api.html): https://l3vnc.catmaid.virtualflybrain.org/apis/
+
+## Citation Guidelines
+
+When using this data, please cite:
+
+1. The L3VNC dataset:
+   Gerhard S, Andrade I, Fetter RD, Cardona A, Schneider-Mizell CM (2017) Conserved neural circuit structure across Drosophila larval development revealed by comparative connectomics. eLife, 6:e29089. https://doi.org/10.7554/eLife.29089
+
+2. The CATMAID platform:
+   Saalfeld S, Cardona A, Hartenstein V, Tomancak P (2009) CATMAID: collaborative annotation toolkit for massive amounts of image data. Bioinformatics 25(15): 1984-1986. https://doi.org/10.1093/bioinformatics/btp266
+
+3. The specific publication(s) associated with any neurons you analyze or reference
+
+## Maintenance & Support
+
+This resource is archived, hosted, and maintained by Virtual Fly Brain (VFB - https://virtualflybrain.org) as part of their commitment to preserving and making accessible critical Drosophila neuroscience data resources.