Introduce enums for items, machines, and recipes, and integrate recipe selection logic. Add .gitignore and improve Flask app for query-based input handling.

templates/index.html

@@ -33,7 +33,7 @@
     <h1>Satisfactory Production Calculator</h1>
     <p>Compute buildings and raw inputs for a target output rate (items per minute). Data set includes a few early-game default recipes; you can extend it in <code>main.py</code>.</p>
 
-    <form class="card" method="post">
+    <form class="card" method="get">
       <div class="row">
         <div>
           <label for="item">Product</label>