fix(minimax-mem0): convert to Agent Plugins 1.0 format (plugin.json + mcp.json at root)

The runtime imports validate against the open Agent Plugins 1.0 spec
(agent-plugins.org), not the Feishu submission guide's .minimax-plugin/ layout.
Discovered via the in-app import (GitHub Plugin cannot be imported).

integrations/minimax-mem0/.minimax-plugin/plugin.json

@@ -1,18 +0,0 @@
-{
-  "schemaVersion": 1,
-  "name": "mem0",
-  "displayName": "Mem0 Memory",
-  "version": "0.1.0",
-  "description": "Persistent long-term memory for your agent: remember preferences, decisions, and project context across sessions, and recall them on demand.",
-  "author": "Mem0",
-  "icon": "icon.png",
-  "category": "Productivity",
-  "exampleQueries": [
-    "Remember that I prefer TypeScript and pnpm",
-    "What do you remember about my project?",
-    "Update what you know about my deployment setup"
-  ],
-  "apps": [],
-  "mcpServers": ["mem0.mcp.json"],
-  "skills": ["skills/memory/SKILL.md"]
-}