Bake VERSION into Docker image so About page shows correct version

Without COPY VERSION, _read_version() fell back to "0.0.0". The volume
mount is a runtime override; the baked-in copy is the reliable baseline.

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

Dockerfile

@@ -24,6 +24,7 @@ RUN pip install --no-cache-dir -r /tmp/requirements.txt
 WORKDIR /app
 COPY server.py .
 COPY CHANGELOG.md .
+COPY VERSION .
 COPY core/ core/
 COPY routes/ routes/
 COPY static/ static/