Fixed #317 - Metric resist balance point is sometimes wrong

Added more precision to profile linear trendline generation.

api/profile.php

@@ -960,8 +960,8 @@ class profile extends cora\api {
     $intercept = (($sum_y) - ($slope * $sum_x)) / ($n);
 
     return [
-      'slope' => round($slope, 2),
-      'intercept' => round($intercept, 2)
+      'slope' => round($slope, 4),
+      'intercept' => round($intercept, 4)
     ];
   }
 }

js/component/card/temperature_profiles.js

@@ -145,6 +145,9 @@ beestat.component.card.temperature_profiles.prototype.get_data_ = function() {
 /**
  * Get a linear trendline from a set of data.
  *
+ * IMPORTANT: This exists in the profile already but it's wrong to use it
+ * directly as it's not right for Celsius.
+ *
  * @param {Object} data The data; at least two points required.
  *
  * @return {Object} The slope and intercept of the trendline.