feat: Menue HW Planung - Materialfluss-Skizze <dwg>_HW.dxf aus dem CSV-Export

HW_MATERIALFLUSS ruft EXPORTCSV und lib/hw_materialfluss.py: Kreisel-Rechtecke
in Drehrichtung, Strecken AS -> Separatoren -> ES, Weichen, Be-/Entladungen.
HW_SYMBOLE vorerst Platzhalter.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

lang/en_GB.json

@@ -1143,6 +1143,9 @@
     "tt-stil": "\nText style",
     "tt-stil-fehlt": "\nText style %1 does not exist in the drawing.",
     "tt-stil-titel": "Change text style",
+    "hw-csv-fehlt": "\n[HW_MATERIALFLUSS] ERROR: CSV export missing: %1 - material flow not created.",
+    "hw-fertig": "\n[HW_MATERIALFLUSS] Material flow written: %1",
+    "hw-symbole-offen": "HW planning - create symbols is not implemented yet.",
     "dinformate-dialog-fehlt": "DIN formats dialog not found: %1",
     "dinformate-datei-fehlt": "DIN formats: file not found: %1",
     "dinformate-prompt-rahmen": "\nBorder insertion point (lower left corner): ",