feat: shadcn -> rust-ui.com migration + TorrentDetail silme

- Tüm leptos-shadcn-* paketleri kaldırıldı (19 dependency)
- leptos_ui, tw_merge, strum eklendi
- components/ui/ modülü oluşturuldu (Button, Card, Input)
- TorrentDetail bileşeni tamamen silindi
- sidebar.rs: saf HTML+Tailwind ile SidebarButton yardımcı bileşeni
- toolbar.rs, login.rs, setup.rs, add_torrent.rs: saf HTML+Tailwind
- table.rs: shadcn Card -> rust-ui Card
- app.rs: Skeleton -> animate-pulse div

frontend/src/components/ui/button.rs

@@ -0,0 +1,29 @@
+use leptos::prelude::*;
+use leptos_ui::variants;
+
+variants! {
+    Button {
+        base: "inline-flex items-center justify-center gap-2 whitespace-nowrap rounded-md text-sm font-medium transition-all disabled:pointer-events-none disabled:opacity-50 [&_svg]:pointer-events-none [&_svg:not([class*='size-'])]:size-4 shrink-0 [&_svg]:shrink-0 outline-none focus-visible:border-ring focus-visible:ring-ring/50 focus-visible:ring-[3px] aria-invalid:ring-destructive/20 dark:aria-invalid:ring-destructive/40 aria-invalid:border-destructive w-fit hover:cursor-pointer active:scale-[0.98] active:opacity-100 touch-manipulation [-webkit-tap-highlight-color:transparent] select-none [-webkit-touch-callout:none]",
+        variants: {
+            variant: {
+                Default: "bg-primary text-primary-foreground shadow-xs hover:bg-primary/90",
+                Destructive: "bg-destructive text-white shadow-xs hover:bg-destructive/90 focus-visible:ring-destructive/20 dark:focus-visible:ring-destructive/40 dark:bg-destructive/60",
+                Outline: "border bg-background shadow-xs hover:bg-accent hover:text-accent-foreground dark:bg-input/30 dark:border-input dark:hover:bg-input/5",
+                Secondary: "bg-secondary text-secondary-foreground shadow-xs hover:bg-secondary/80",
+                Ghost: "hover:bg-accent hover:text-accent-foreground dark:hover:bg-accent/50",
+                Link: "text-primary underline-offset-4 hover:underline",
+            },
+            size: {
+                Default: "h-9 px-4 py-2 has-[>svg]:px-3",
+                Sm: "h-8 rounded-md gap-1.5 px-3 has-[>svg]:px-2.5",
+                Lg: "h-10 rounded-md px-6 has-[>svg]:px-4",
+                Icon: "size-9",
+            }
+        },
+        component: {
+            element: button,
+            support_href: true,
+            support_aria_current: true
+        }
+    }
+}