fix: URL-encode asset filename, truncate error body in APIError

- URL-encode filename in release upload query param (MINOR)
- Truncate APIError.Body to 200 chars in Error() to avoid leaking
  verbose server responses into logs (NIT)

gitea/client.go

@@ -26,7 +26,11 @@ type APIError struct {
 }
 
 func (e *APIError) Error() string {
-	return fmt.Sprintf("HTTP %d: %s", e.StatusCode, e.Body)
+	body := e.Body
+	if len(body) > 200 {
+		body = body[:200] + "...(truncated)"
+	}
+	return fmt.Sprintf("HTTP %d: %s", e.StatusCode, body)
 }
 
 // IsNotFound reports whether an error is an API 404 response.