Fix Twilio MCP integration with baked-in credentials

- Add proper type and env sections to mcp-config.json
- Remove dynamic MCP add command, use pre-configured MCP
- Bake .env credentials into Docker image at build time
- Remove runtime .env volume mount - true one-time setup
- Auto-rebuild image when .env file changes
- Export Twilio env vars for MCP server subprocess
- Remove conflicting .mcp.json file

config/mcp-config.json

@@ -1,6 +1,7 @@
 {
   "mcpServers": {
     "twilio": {
+      "type": "stdio",
       "command": "npx",
       "args": [
         "-y",
@@ -10,7 +11,14 @@
         "twilio_api_v2010",
         "--tags",
         "Api20100401Message"
-      ]
+      ],
+      "env": {
+        "TWILIO_ACCOUNT_SID": "${TWILIO_ACCOUNT_SID}",
+        "TWILIO_API_KEY": "${TWILIO_API_KEY}",
+        "TWILIO_API_SECRET": "${TWILIO_API_SECRET}",
+        "TWILIO_FROM_NUMBER": "${TWILIO_FROM_NUMBER}",
+        "TWILIO_TO_NUMBER": "${TWILIO_TO_NUMBER}"
+      }
     }
   }
 }