Add env example

.env.example

@@ -0,0 +1,8 @@
+# Copy to .env and adjust for your deployment
+SECRET_KEY=change-me-to-a-long-random-string
+ACCESS_TOKEN_EXPIRE_MINUTES=1440
+DATABASE_URL=sqlite:///./trainhub.db
+STORAGE_DIR=./storage
+# Optional: your HF token to enable authenticated Hub push / increased rate limits
+HF_TOKEN=
+PUBLIC_DOMAIN=http://localhost:8000