switch DEBUG_LOG to string handling

src/lib/log.ts

@@ -4,6 +4,7 @@ import { isTruthy } from '$lib/truthyString';
 const { DEV } = import.meta.env;
 
 export const enableVerboseLog = isTruthy(env.VERBOSE);
+export const debugLogEnv = isTruthy(DEBUG_LOG);
 
 /**
  * @deprecated Use the new {@link Logger} class instead.
@@ -42,7 +43,7 @@ export class Logger {
   public constructor(private name: string) {}
 
   public static isDebugEnabled(): boolean {
-    return !!DEBUG_LOG || DEV || enableVerboseLog;
+    return debugLogEnv || DEV || enableVerboseLog;
   }
   public verbose(...params: any[]) {
     if (!enableVerboseLog) {

src/lib/truthyString.ts

@@ -1,4 +1,7 @@
 export function isTruthy(value: string | number | boolean | null | undefined): boolean {
+  if (value === null || value === undefined) {
+    return false;
+  }
   if (typeof value === 'string') {
     return value.toLowerCase() === 'true' || !!+value; // here we parse to number first
   }