fix(dwg): correct ODA download URL + dynamic binary path lookup

- Use www.opendesign.com/guestfiles/get URL (no auth required)
- Auto-find and symlink ODA binary after dpkg install
- app.py searches multiple common install paths

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

dwg2dxf-api/Dockerfile

@@ -1,6 +1,6 @@
 FROM ubuntu:24.04
 
-# ODA File Converter needs Qt libs + virtual framebuffer for headless mode
+# Qt libs + virtual framebuffer for headless ODA File Converter
 RUN apt-get update && \
     apt-get install -y --no-install-recommends \
         python3 python3-pip wget ca-certificates \
@@ -10,14 +10,17 @@ RUN apt-get update && \
         libglib2.0-0 libgl1 libfontconfig1 libfreetype6 && \
     pip3 install --no-cache-dir --break-system-packages flask && \
     apt-get purge -y python3-pip && \
-    apt-get autoremove -y && \
-    rm -rf /var/lib/apt/lists/*
+    apt-get autoremove -y
 
 # Download and install ODA File Converter
-RUN wget -q "https://download.opendesign.com/guestfiles/Demo/ODAFileConverter_QT6_lnxX64_8.3dll_25.12.deb" \
+RUN wget -q "https://www.opendesign.com/guestfiles/get?filename=ODAFileConverter_QT6_lnxX64_8.3dll_27.1.deb" \
         -O /tmp/oda.deb && \
     dpkg -i /tmp/oda.deb || apt-get install -f -y && \
-    rm /tmp/oda.deb
+    rm /tmp/oda.deb && \
+    rm -rf /var/lib/apt/lists/* && \
+    # Find the binary and symlink to /usr/local/bin for PATH access
+    find / -name "ODAFileConverter" -type f -executable 2>/dev/null | head -1 | \
+        xargs -I{} ln -sf {} /usr/local/bin/ODAFileConverter
 
 WORKDIR /app
 COPY app.py .