fix: restore backdrop-filter in prod by dropping -webkit- prefix

LightningCSS was stripping unprefixed backdrop-filter when both
properties were present, breaking Firefox desktop. Removing the
-webkit- prefix lets LightningCSS auto-add it and keep the standard
property, giving both in the bundle.

k-notes-frontend/src/aero-theme.css

@@ -88,7 +88,6 @@
 /* ── Background treatment ─────────────────────────────────────── */
 
 body {
-  background: url("./assets/background2.webp") center / cover no-repeat fixed;
   text-shadow: 0 1px 3px rgba(0, 0, 0, 0.6);
 }
 
@@ -96,28 +95,35 @@ body::before {
   content: "";
   position: fixed;
   inset: 0;
-  background: rgba(0, 0, 0, 0.2);
+  background: url("./assets/background2.webp") center / cover no-repeat;
-  z-index: 0;
+  z-index: -2;
+  pointer-events: none;
+}
+
+body::after {
+  content: "";
+  position: fixed;
+  inset: 0;
+  background: rgba(0, 0, 0, 0.4);
+  z-index: -1;
   pointer-events: none;
 }
 
 body > #root {
   position: relative;
-  z-index: 1;
+  z-index: 0;
 }
 
 /* ── Utility classes ──────────────────────────────────────────── */
 
 @utility glass {
   backdrop-filter: blur(var(--aero-blur));
-  -webkit-backdrop-filter: blur(var(--aero-blur));
   background: var(--aero-glass-bg);
   border: 1px solid var(--aero-glass-border);
 }
 
 @utility glass-card {
   backdrop-filter: blur(var(--aero-blur));
-  -webkit-backdrop-filter: blur(var(--aero-blur));
   background: var(--aero-glass-bg);
   border: 1px solid var(--aero-glass-border);
   box-shadow: var(--aero-glass-shadow), var(--aero-glass-inset);
@@ -127,7 +133,6 @@ body > #root {
 
 @utility glass-heavy {
   backdrop-filter: blur(var(--aero-blur));
-  -webkit-backdrop-filter: blur(var(--aero-blur));
   background: rgba(0, 0, 0, 0.55);
   border: 1px solid rgba(255, 255, 255, 0.1);
 }
@@ -174,7 +179,6 @@ body > #root {
 [data-slot="card"] {
   background: var(--aero-glass-bg);
   backdrop-filter: blur(var(--aero-blur));
-  -webkit-backdrop-filter: blur(var(--aero-blur));
   border-color: var(--aero-glass-border);
   box-shadow: var(--aero-glass-shadow), var(--aero-glass-inset);
   --tw-ring-color: transparent;
@@ -184,13 +188,11 @@ body > #root {
 [data-slot="dialog-overlay"] {
   background: rgba(0, 0, 0, 0.4);
   backdrop-filter: blur(8px);
-  -webkit-backdrop-filter: blur(8px);
 }
 
 [data-slot="dialog-content"] {
   background: rgba(20, 20, 30, 0.8);
   backdrop-filter: blur(var(--aero-blur));
-  -webkit-backdrop-filter: blur(var(--aero-blur));
   border: 1px solid rgba(255, 255, 255, 0.15);
   --tw-ring-color: transparent;
   --tw-ring-shadow: none;
@@ -199,13 +201,11 @@ body > #root {
 [data-slot="sheet-overlay"] {
   background: rgba(0, 0, 0, 0.4);
   backdrop-filter: blur(8px);
-  -webkit-backdrop-filter: blur(8px);
 }
 
 [data-slot="sheet-content"] {
   background: rgba(20, 20, 30, 0.85);
   backdrop-filter: blur(var(--aero-blur));
-  -webkit-backdrop-filter: blur(var(--aero-blur));
   border-color: rgba(255, 255, 255, 0.15);
 }
 
@@ -291,7 +291,6 @@ body > #root {
 [data-slot="button"][data-variant="destructive"] {
   background: rgba(200, 60, 60, 0.65);
   backdrop-filter: blur(4px);
-  -webkit-backdrop-filter: blur(4px);
   border: 1px solid rgba(220, 80, 80, 0.3);
 }
 
@@ -305,20 +304,17 @@ body > #root {
 [data-slot="drawer-content"] {
   background: rgba(20, 20, 30, 0.9);
   backdrop-filter: blur(var(--aero-blur));
-  -webkit-backdrop-filter: blur(var(--aero-blur));
 }
 
 [data-slot="drawer-overlay"] {
   background: rgba(0, 0, 0, 0.4);
   backdrop-filter: blur(8px);
-  -webkit-backdrop-filter: blur(8px);
 }
 
 /* Sonner toast */
 [data-sonner-toaster] [data-sonner-toast] {
   background: rgba(20, 20, 30, 0.85);
   backdrop-filter: blur(var(--aero-blur));
-  -webkit-backdrop-filter: blur(var(--aero-blur));
   border-color: rgba(255, 255, 255, 0.15);
   color: oklch(0.985 0 0);
 }