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>

mcp-bridge/package.json

@@ -0,0 +1,13 @@
+{
+  "name": "mcp-bridge",
+  "version": "1.0.0",
+  "description": "Generic MCP SSE bridge for the MCP hub",
+  "main": "index.js",
+  "scripts": {
+    "start": "node index.js"
+  },
+  "dependencies": {
+    "ws": "^8.19.0"
+  },
+  "license": "ISC"
+}