Fix Docker database directory and permissions

- Create /db directory in container
- Ensure database directory exists and has proper permissions in startup script
- Remove problematic conditional COPY command that was causing build failures

This fixes the 'unable to open database file' error by ensuring the
database directory exists before migrations run.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

Dockerfile

@@ -91,17 +91,17 @@ COPY --from=backend-builder /usr/local/cargo/bin/sqlx /usr/local/bin/sqlx
 # Copy migrations for database setup
 COPY --from=backend-builder /app/backend/migrations /migrations
 
-# Copy existing database if it exists (optional - migrations will create if needed)
-COPY --from=backend-builder /app/backend/calendar.db /calendar.db 2>/dev/null || true
-
 # Create startup script to copy frontend files, run migrations, and start backend
-RUN mkdir -p /srv/www
+RUN mkdir -p /srv/www /db
 RUN echo '#!/bin/sh' > /usr/local/bin/start.sh && \
     echo 'echo "Copying frontend files..."' >> /usr/local/bin/start.sh && \
     echo 'cp -r /app/frontend-dist/* /srv/www/' >> /usr/local/bin/start.sh && \
+    echo 'echo "Ensuring database directory exists..."' >> /usr/local/bin/start.sh && \
+    echo 'mkdir -p /db && chmod 755 /db' >> /usr/local/bin/start.sh && \
     echo 'echo "Running database migrations..."' >> /usr/local/bin/start.sh && \
-    echo 'sqlx migrate run --database-url "sqlite:/calendar.db" --source /migrations || echo "Migration failed but continuing..."' >> /usr/local/bin/start.sh && \
+    echo 'sqlx migrate run --database-url "sqlite:/db/calendar.db" --source /migrations || echo "Migration failed but continuing..."' >> /usr/local/bin/start.sh && \
     echo 'echo "Starting backend server..."' >> /usr/local/bin/start.sh && \
+    echo 'export DATABASE_URL="sqlite:/db/calendar.db"' >> /usr/local/bin/start.sh && \
     echo '/usr/local/bin/backend' >> /usr/local/bin/start.sh && \
     chmod +x /usr/local/bin/start.sh