Add material flow generator for the mechanical layout

Reads the CSV export of the plant objects (ILS 2.0) from SKEL_DATA and builds a
directed graph of the material flow, written as Graphviz DOT and optionally SVG
into SKEL_RESULTS.

Node model: one node per Gefaellestrecke and Strecke; a Kreisel becomes two
nodes (-L / -R) wired into a circle, since it is a carousel with one lane per
travel direction. Separators and scanners are no nodes of their own; they are
shown on the label of the object they are assigned to.

Edge direction is not in the CSV - the Nachbarn column is symmetric. It is
derived from geometry instead: a Gefaellestrecke runs downhill away from its
highest neighbour, a driven Strecke follows Antriebfahrtrichtung ("Auf" uphill,
"Ab" downhill). Connections that stay ambiguous, e.g. between two Kreisel at the
same height, are drawn as bidirectional edges and reported.

The lane suffix of a Kreisel is always stated in the *partner's* row, so both
viewpoints of a link are merged before orienting it.

Switches:
  --file   name of the CSV in SKEL_DATA, or a full path
  --tosvg  render the DOT via Graphviz
  --doc    write a Markdown documentation of the plant objects

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

bin/material_flow.bat

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+@echo off
+REM ================================================================
+REM SPS_SKEL - Materialfluss-Graph erzeugen
+REM ================================================================
+REM Aufruf:
+REM   bin\material_flow.bat --file export.csv
+REM   bin\material_flow.bat --file export.csv --tosvg
+REM
+REM Die CSV-Datei wird in %SKEL_DATA% gesucht, DOT und SVG werden
+REM in %SKEL_RESULTS% abgelegt.
+REM ================================================================
+
+setlocal
+
+REM Umgebung setzen (SKEL_DATA, SKEL_RESULTS, SKEL_LIB, PYTHONPATH ...)
+call "%~dp0setenv.bat" >nul
+
+REM Virtuelle Umgebung nutzen, falls vorhanden
+if exist "%SPS_SKEL%\.venv\Scripts\activate.bat" (
+    call "%SPS_SKEL%\.venv\Scripts\activate.bat"
+)
+
+REM Python-Interpreter bestimmen (py-Launcher bevorzugt, sonst python)
+set "PY=py"
+py --version >nul 2>&1 || set "PY=python"
+
+"%PY%" "%SKEL_LIB%\material_flow.py" %*
+set "RC=%ERRORLEVEL%"
+
+endlocal & exit /b %RC%

bin/material_flow.sh

@@ -0,0 +1,31 @@
+#!/usr/bin/env bash
+# ================================================================
+# SPS_SKEL - Materialfluss-Graph erzeugen
+# ================================================================
+# Aufruf:
+#   bash bin/material_flow.sh --file export.csv
+#   bash bin/material_flow.sh --file export.csv --tosvg
+#
+# Die CSV-Datei wird in $SKEL_DATA gesucht, DOT und SVG werden
+# in $SKEL_RESULTS abgelegt.
+# ================================================================
+
+set -eu
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+
+# Umgebung setzen (SKEL_DATA, SKEL_RESULTS, SKEL_LIB, PYTHONPATH ...)
+# shellcheck source=/dev/null
+. "$SCRIPT_DIR/setenv.sh" >/dev/null
+
+# Virtuelle Umgebung nutzen, falls vorhanden
+if [ -f "$SPS_SKEL/.venv/bin/activate" ]; then
+    # shellcheck source=/dev/null
+    . "$SPS_SKEL/.venv/bin/activate"
+fi
+
+# Python-Interpreter bestimmen
+PY="python3"
+command -v python3 >/dev/null 2>&1 || PY="python"
+
+exec "$PY" "$SKEL_LIB/material_flow.py" "$@"