Access permissions, seed permissions, security, session, api/session improved handling + speed across the site/UX improvements

frontend/src/routes/mix-calculator/+page.svelte

@@ -18,16 +18,11 @@
   }
 </script>
 
-<section class="page-intro">
-  <div>
-    <p class="eyebrow">Mix Calculator</p>
-    <h2>Saved production sessions</h2>
-    <p>Each session preserves the scaled raw material output so it can be reopened or printed later without relying on live recipe changes.</p>
-  </div>
-  {#if canEdit}
+{#if canEdit}
+  <section class="page-actions">
     <a class="primary-button" href="/mix-calculator/new">New mix session</a>
-  {/if}
-</section>
+  </section>
+{/if}
 
 <section class="metric-row">
   <article class="metric-card">
@@ -123,27 +118,17 @@
     text-transform: uppercase;
   }
 
-  .page-intro,
+  .page-actions,
   .metric-row,
   .table-card {
     margin-bottom: 1.25rem;
   }
 
-  .page-intro {
+  .page-actions {
     display: flex;
-    align-items: flex-start;
-    justify-content: space-between;
-    gap: 1rem;
+    justify-content: flex-end;
   }
 
-  .page-intro h2 {
-    margin: 0.35rem 0 0.45rem;
-    max-width: 15ch;
-    font-size: clamp(1.7rem, 3vw, 2.2rem);
-    font-weight: 700;
-  }
-
-  .page-intro p:last-child,
   .metric-card p,
   .table-toolbar p,
   tbody span {
@@ -283,7 +268,6 @@
   }
 
   @media (max-width: 760px) {
-    .page-intro,
     .table-toolbar {
       flex-direction: column;
       align-items: flex-start;