add achats import and hardware analyse

frontend/assets/css/main.css

@@ -2,6 +2,32 @@
   --bg: #f5f1e8;
   --text: #1f1b16;
   --accent: #c46b2d;
+  --card: #fffaf2;
+  --border: #e3d8c5;
+}
+
+html[data-theme="dark"] {
+  --bg: #1c1a17;
+  --text: #f2e7d5;
+  --accent: #e29a4f;
+  --card: #26231e;
+  --border: #3b342c;
+}
+
+html[data-theme="monokai"] {
+  --bg: #272822;
+  --text: #f8f8f2;
+  --accent: #a6e22e;
+  --card: #2e2f28;
+  --border: #3d3e36;
+}
+
+html[data-theme="gruvbox-dark"] {
+  --bg: #282828;
+  --text: #ebdbb2;
+  --accent: #d79921;
+  --card: #32302f;
+  --border: #504945;
 }
 
 * {
@@ -11,7 +37,7 @@
 body {
   margin: 0;
   font-family: "Space Grotesk", system-ui, sans-serif;
-  background: linear-gradient(135deg, #f5f1e8 0%, #efe6d6 100%);
+  background: linear-gradient(135deg, var(--bg) 0%, color-mix(in srgb, var(--bg) 85%, #000 15%) 100%);
   color: var(--text);
 }
 
@@ -77,10 +103,10 @@ a {
 }
 
 .card {
-  border: 1px solid #e3d8c5;
+  border: 1px solid var(--border);
   border-radius: 16px;
   padding: 16px;
-  background: #fffaf2;
+  background: var(--card);
   box-shadow: 0 8px 20px rgba(60, 40, 20, 0.08);
 }