fix: simplify disco.json to use Dockerfile build process

Remove custom build commands and worker service from disco.json to avoid
conflicts with vendor/aprs dependency compilation. Let Disco use the
existing Dockerfile which properly handles the build process.

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

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

disco.json

@@ -2,18 +2,7 @@
   "version": "1.0",
   "services": {
     "web": {
-      "port": 4000,
-      "command": "mix phx.server"
-    },
-    "worker": {
-      "command": "mix run --no-halt"
-    }
-  },
-  "build": {
-    "command": "mix assets.deploy && mix release",
-    "env": {
-      "MIX_ENV": "prod",
-      "PHX_SERVER": "true"
+      "port": 4000
     }
   }
 }