docs: merge the Fleet docs into backend/fleet/README.md, add TODO.md, unify the Backend compose, fix stale references [CI SKIP]

packaging/compose/backend/compose.yaml

@@ -1,15 +0,0 @@
-# Docker / Podman 共用，数据库和原始数据保存在命名 volume 中。
-services:
-  backend:
-    image: ${MOSHIRO_IMAGE:-registry.oeo.one/moshiro/moshiro-backend}:${MOSHIRO_VERSION:-0.1.1}
-    container_name: moshiro-backend
-    restart: unless-stopped
-    ports:
-      - "127.0.0.1:8080:8080"
-    environment:
-      MoShiro__InitialAdminPassword: ${MOSHIRO_INITIAL_ADMIN_PASSWORD:?Set MOSHIRO_INITIAL_ADMIN_PASSWORD}
-    volumes:
-      - backend-data:/data
-volumes:
-  backend-data:
-    name: moshiro-backend-data