Add app.json to override Django predeploy task

- Remove Django manage.py migrate predeploy task
- Add proper health check configuration for Go API

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

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

app.json

@@ -0,0 +1,18 @@
+{
+  "name": "mycrib-api",
+  "description": "MyCrib API (Go)",
+  "scripts": {},
+  "healthchecks": {
+    "web": [
+      {
+        "type": "startup",
+        "name": "web check",
+        "path": "/api/health/",
+        "attempts": 3,
+        "wait": 5,
+        "timeout": 30,
+        "content": "healthy"
+      }
+    ]
+  }
+}