feat: add generic mcp-bridge for proxying upstream MCP SSE servers

- Add mcp-bridge/index.js: WebSocket backend for hub, relays requests
  to upstream MCP SSE servers via SSE+POST transport
- Add mcp-bridge/package.json with 'ws' dependency
- Add 'mcp-bridge-memory' entry to ecosystem.config.js (not started)
- Add 'bridge' script to root package.json
- Add mcp-bridge/node_modules to .gitignore

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

ecosystem.config.js

@@ -19,6 +19,17 @@ module.exports = {
       restart_delay: 2000,
       log_date_format: 'YYYY-MM-DD HH:mm:ss Z',
       merge_logs: true
+    },
+    {
+      name: 'mcp-bridge-memory',
+      script: 'mcp-bridge/index.js',
+      cwd: '/workspace',
+      env: {
+        BRIDGE_SERVICE_ID: 'memory-mcp',
+        BRIDGE_SECRET: 'dev-secret',
+        BRIDGE_HUB_URL: 'ws://localhost:3000/ws/register',
+        BRIDGE_UPSTREAM_URL: 'https://memory-mcp.dbchat.ai/mcp/sse'
+      }
     }
   ]
 };