uv pip install --system installs packages globally but uv run still
tries to create /app/.venv, which fails with permission denied.
Add PYTHONPATH=/app/src since the editable install .pth file is empty
when built without source directory present.
Notebook cards now show schematic SVG thumbnails (on Mims green background)
and description snippets extracted from the first markdown cell. The backend
extracts both from already-loaded notebook data at zero additional I/O cost.
New ResistorColorGuide section between the pipeline strip and featured
notebooks explains the 4-band color code with an annotated zigzag diagram
and reference table using the same BAND_HEX colors from the schematic renderer.
Also switches docker-compose.dev.yml from direct port mapping to Caddy labels,
matching the production routing pattern and avoiding port conflicts.
