routes: use detected base URL in usage examples

app/api/routes.py

@@ -23,6 +23,22 @@ def _url(path: str) -> str:
     prefix = current_app.config.get("URL_PREFIX", "")
     return f"{prefix}{path}"
 
+
+def _base_url() -> str:
+    """Detect base URL from request headers (for reverse proxy deployments)."""
+    scheme = (
+        request.headers.get("X-Forwarded-Proto")
+        or request.headers.get("X-Scheme")
+        or request.scheme
+    )
+    host = (
+        request.headers.get("X-Forwarded-Host")
+        or request.headers.get("Host")
+        or request.host
+    )
+    prefix = current_app.config.get("URL_PREFIX", "")
+    return f"{scheme}://{host}{prefix}"
+
 # Runtime-generated PoW secret (used if not configured)
 _pow_secret_cache = None
 
@@ -341,9 +357,9 @@ def index():
                 f"DELETE {_url('/<id>')}": "Delete paste",
             },
             "usage": {
-                "raw": f"curl --data-binary @file.txt http://host{_url('/')}",
-                "pipe": f"cat file.txt | curl --data-binary @- http://host{_url('/')}",
-                "json": f"curl -H 'Content-Type: application/json' -d '{{\"content\":\"...\"}}' http://host{_url('/')}",
+                "raw": f"curl --data-binary @file.txt {_base_url()}/",
+                "pipe": f"cat file.txt | curl --data-binary @- {_base_url()}/",
+                "json": f"curl -H 'Content-Type: application/json' -d '{{\"content\":\"...\"}}' {_base_url()}/",
             },
             "note": "Use --data-binary (not -d) to preserve newlines",
         }