moved basic talent properties in talent-sheet head

- a little bit better gridding of side-properties
  (still needs a rewrite)
- common SCSS mixin for input field marking

src/scss/utils/_mixins.scss

@@ -19,3 +19,12 @@
     display: grid;
     place-items: center;
 }
+
+@mixin mark-invalid-or-disabled-input {
+    input:invalid {
+        background-color: $c-invalid-input;
+    }
+    input:disabled {
+        background-color: transparent;
+    }
+}