Restructure mobile task manager as /tasks folder (like /admin)

Moved tasks.html to tasks/index.html
Updated 11ty to copy tasks/ folder
Now accessible at firefrostgaming.com/tasks (no .html extension needed)

Matches the pattern used by /admin for Decap CMS.

.eleventy.js

@@ -8,7 +8,7 @@ module.exports = function(eleventyConfig) {
   eleventyConfig.addPassthroughCopy("admin");
   
   // Mobile task manager
-  eleventyConfig.addPassthroughCopy("tasks.html");
+  eleventyConfig.addPassthroughCopy("tasks");
 
   return {
     dir: {