fix: VERSION généré par build.sh avant docker build (pas dans Dockerfile)

- build.sh: git describe --tags --dirty > backend/VERSION avant docker compose build
- Dockerfile: COPY backend/VERSION (pré-généré, plus fiable que .git dans le contexte)
- .dockerignore: revert (plus besoin d'autoriser .git/HEAD)
- .gitignore: backend/VERSION (généré, pas commité)

Dockerfile

@@ -31,21 +31,8 @@ RUN apt-get update \
 COPY backend/ ./backend/
 COPY frontend/ ./frontend/
 
-# Generate VERSION file from git (fallback for version.py when .git is not available)
-COPY .git/HEAD .git/refs/ /tmp/git-refs/
-RUN cd /tmp/git-refs && \
-    if [ -f HEAD ]; then \
-      REF=$(cat HEAD | awk '{print $2}'); \
-      if [ -f "$REF" ]; then \
-        HASH=$(cat "$REF" | head -c 8); \
-        echo "1.8.0-0-g${HASH}" > /app/backend/VERSION; \
-      else \
-        echo "1.8.0-dev" > /app/backend/VERSION; \
-      fi; \
-    else \
-      echo "1.8.0-dev" > /app/backend/VERSION; \
-    fi && \
-    rm -rf /tmp/git-refs
+# Copy pre-generated VERSION file (generated by build.sh before docker build)
+COPY backend/VERSION ./backend/VERSION
 
 # Create non-root user for security + data directory for auth persistence
 # Using explicit UID/GID 1000 to match common host user and docker-compose settings