refactor: config/apps 目录重组、文档重构、架构图收窄

- 中央：config/(prometheus,alertmanager,grafana)、apps/(tile-cache,topology-editor)
- 边缘：config/(vmagent,blackbox,targets)、apps/(onvif-exporter)
- env: TRAEFIK_PROVIDER、prometheus/env.example 详细说明
- 文档：README/doc 重构，EDGE_CACHE 合并到 EDGE_AGENT_CONFIG
- targets.csv 更新流程说明，ARCHITECTURE 图收窄

Made-with: Cursor

central-server/config/grafana/provisioning/datasources/prometheus.yml

@@ -0,0 +1,9 @@
+apiVersion: 1
+
+datasources:
+  - name: Prometheus
+    type: prometheus
+    access: proxy
+    url: http://prometheus-central:9090
+    isDefault: true
+    editable: true