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

.env.example

@@ -0,0 +1,21 @@
+#
+# Project-root Docker/Compose overrides
+# Copy to `.env` only when you need custom ports or want to switch image source.
+#
+
+# Optional custom ports
+# FRONTEND_PORT=8888
+# BACKEND_PORT=127.0.0.1:5000
+# DB_PORT=127.0.0.1:5432
+
+# Global image source switch
+# Leave empty for official Docker Hub:
+# IMAGE_PREFIX=
+#
+# Common alternatives (pick one, keep trailing slash):
+# IMAGE_PREFIX=docker.m.daocloud.io/library/
+# IMAGE_PREFIX=docker.xuanyuan.me/library/
+#
+# Important:
+# - This file lives in the project root and is used by docker-compose build/pull.
+# - `backend_api_python/.env` is runtime config for the backend container only.