feat(templates): document templating system with Save as Template command
Add a template system that lets users create new items from pre-configured
.kc template files and save existing documents as reusable templates.
Template use (New Item form):
- templates.py: discovery, filtering, TemplateInfo dataclass
- schema_form.py: template combo picker filtered by type/category
- silo_commands.py: SiloSync.create_document_from_template() copies
template .kc, strips identity, stamps Silo properties
Template creation (Save as Template):
- SaveAsTemplateDialog: captures name, description, item types,
categories, author, and tags
- Silo_SaveAsTemplate command: copies doc, strips Silo identity,
injects silo/template.json, optionally uploads to Silo
- Registered in Silo menu via InitGui.py
Template search paths (3-tier, later shadows earlier by name):
1. mods/silo/freecad/templates/ (system)
2. ~/.local/share/FreeCAD/Templates/ (personal, sister to Macro/)
3. ~/projects/templates/ (org-shared)
a88e104d94