feat: restore cmdb-assistant plugin and fix marketplace paths

- Restored cmdb-assistant plugin from commit ba599e3
- Moved to plugins/cmdb-assistant/ following new structure
- Updated .mcp.json path to ../../mcp-servers/netbox
- Fixed marketplace.json paths for all plugins (now in plugins/)
- Updated README.md with cmdb-assistant link and structure
- Updated CLAUDE.md governance to include cmdb-assistant

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.claude-plugins/projman-marketplace/.claude-plugin/marketplace.json

@@ -9,19 +9,19 @@
       "name": "projman",
       "version": "0.1.0",
       "description": "Sprint planning and project management with Gitea and Wiki.js integration",
-      "source": "./../../projman"
+      "source": "./../../../plugins/projman"
     },
     {
       "name": "project-hygiene",
       "version": "0.1.0",
       "description": "Post-task cleanup hook that removes temp files, warns about unexpected root files, and manages orphans",
-      "source": "./../../project-hygiene"
+      "source": "./../../../plugins/project-hygiene"
     },
     {
       "name": "cmdb-assistant",
       "version": "1.0.0",
       "description": "NetBox CMDB integration for infrastructure management - query, create, update, and manage network devices, IP addresses, sites, and more",
-      "source": "./../../cmdb-assistant"
+      "source": "./../../../plugins/cmdb-assistant"
     }
   ]
 }