feat: 完善 entries/ 格式 — 补全结构化字段、更新 README 和 Schema

- 所有 20 个 manifest.json 补全旧格式中的结构化字段
  - docker-app: category, fullDesc, stars, githubUrl, install
  - mcp: capabilities, toolCount, install, connection
  - http-api: endpoint, capabilities
- README 全面重写：entries/ 目录结构、manifest 字段说明、三种类型的添加示例
- SCHEMA_VERSION 升级 2.0.0 → 3.0.0
- 根 manifest.json 简化为 entries 统一统计

entries/ragflow-pipeline/manifest.json

@@ -15,5 +15,13 @@
     "macos",
     "windows",
     "linux"
-  ]
+  ],
+  "endpoint": "http://localhost:9380/api/v1",
+  "capabilities": [
+    "doc_parsing",
+    "deep_retrieval",
+    "citation"
+  ],
+  "sourceAppId": "ragflow",
+  "sourceAppName": "RagFlow"
 }