refactor deployment config and exchange integrations

Simplify runtime configuration and remove legacy database and settings surface so new installs are easier to operate.
Refresh deployment assets, docs, and order execution behavior to keep the packaged app aligned with the current backend.

Made-with: Cursor

backend_api_python/Dockerfile

@@ -1,5 +1,7 @@
 # QuantDinger Backend API Dockerfile
-FROM python:3.12-slim-bookworm
+# BASE_IMAGE can be overridden from docker-compose/.env.
+ARG BASE_IMAGE=python:3.12-slim-bookworm
+FROM ${BASE_IMAGE}
 
 # Set working directory
 WORKDIR /app
@@ -31,7 +33,8 @@ COPY . .
 
 # Copy and set up entrypoint script
 COPY docker-entrypoint.sh /usr/local/bin/
-RUN chmod +x /usr/local/bin/docker-entrypoint.sh
+RUN sed -i 's/\r$//' /usr/local/bin/docker-entrypoint.sh \
+    && chmod +x /usr/local/bin/docker-entrypoint.sh
 
 # Create log and data directories
 RUN mkdir -p logs data/memory