fix(quadratic_fit): 拟合过程使用双精度浮点，避免精度丢失

Author: meng-plus

src/algorithms/polyfit.c

@@ -130,7 +130,7 @@ void find_max_y_x(double coef[4], double x_min, double x_max, double *x_max_y, d
 }
 void linear_curve_fit(float *x, float *y, int size, float *slope, float *intercept)
 {
-    float sum_x = 0, sum_y = 0, sum_xy = 0, sum_x2 = 0;
+    double sum_x = 0, sum_y = 0, sum_xy = 0, sum_x2 = 0;
 
     for (int i = 0; i < size; i++)
     {
@@ -146,13 +146,13 @@ void linear_curve_fit(float *x, float *y, int size, float *slope, float *interce
 // 二次拟合函数
 void quadratic_fit(float *x, float *y, int n, float *coeff)
 {
-    float sum_x = 0, sum_x2 = 0, sum_x3 = 0, sum_x4 = 0;
-    float sum_y = 0, sum_xy = 0, sum_x2y = 0;
+    double sum_x = 0, sum_x2 = 0, sum_x3 = 0, sum_x4 = 0;
+    double sum_y = 0, sum_xy = 0, sum_x2y = 0;
 
     for (int i = 0; i < n; i++)
     {
-        float xi  = x[i];
-        float yi  = y[i];
+        double xi  = x[i];
+        double yi  = y[i];
         sum_x    += xi;
         sum_x2   += xi * xi;
         sum_x3   += xi * xi * xi;
@@ -162,20 +162,20 @@ void quadratic_fit(float *x, float *y, int n, float *coeff)
         sum_x2y  += xi * xi * yi;
     }
 
-    float A[3][3] = {
+    double A[3][3] = {
         {     n,  sum_x, sum_x2},
         { sum_x, sum_x2, sum_x3},
         {sum_x2, sum_x3, sum_x4}
     };
 
-    float B[3] = {sum_y, sum_xy, sum_x2y};
+    double B[3] = {sum_y, sum_xy, sum_x2y};
 
     // 解线性方程组
     for (int i = 0; i < 3; i++)
     {
         for (int j = i + 1; j < 3; j++)
         {
-            float ratio = A[j][i] / A[i][i];
+            double ratio = A[j][i] / A[i][i];
             for (int k = 0; k < 3; k++) { A[j][k] -= ratio * A[i][k]; }
             B[j] -= ratio * B[i];
         }
@@ -230,8 +230,8 @@ int calculateBoundedExtremum(const float coeff[3], float x_min, float x_max, flo
     else
     {
         // 极值点在范围外，计算两个端点的值
-        float y_min = coeff[0] + coeff[1] * x_min + coeff[2] * x_min * x_min;
-        float y_max = coeff[0] + coeff[1] * x_max + coeff[2] * x_max * x_max;
+        double y_min = coeff[0] + coeff[1] * x_min + coeff[2] * x_min * x_min;
+        double y_max = coeff[0] + coeff[1] * x_max + coeff[2] * x_max * x_max;
 
         if (coeff[2] > 0)
         {