fix: give the MCP service its own railway.json so it builds mcp-server/Dockerfile

The repo-root railway.json is backend-specific (dockerfilePath: backend/Dockerfile).
Railway feeds it to both services by default, so the MCP service was building the
backend image and running `uvicorn main:app` -- but mcp-server/ has no main.py, only
server.py. Every MCP deploy since #296 crashed at boot ("Could not import module main")
and failed healthcheck, leaving the service frozen on a 2-month-old image. This adds a
dedicated mcp-server/railway.json (build mcp-server/Dockerfile, healthcheck /health) so
the two services stop sharing one backend-shaped config.

Activation: set the MCP service's config-as-code path to mcp-server/railway.json in the
Railway dashboard; the backend service keeps reading the repo-root railway.json.

Author: DevanshuNEU

mcp-server/railway.json

@@ -0,0 +1,14 @@
+{
+  "$schema": "https://railway.app/railway.schema.json",
+  "build": {
+    "builder": "DOCKERFILE",
+    "dockerfilePath": "mcp-server/Dockerfile",
+    "buildContext": "mcp-server"
+  },
+  "deploy": {
+    "restartPolicyType": "ON_FAILURE",
+    "restartPolicyMaxRetries": 10,
+    "healthcheckPath": "/health",
+    "healthcheckTimeout": 300
+  }
+}