fix: dashboard switcher, platform-aware search shortcut, mobile search, static topbar

- Always show dashboard tab strip + add button (was gated behind length > 1)
- Search shortcut now shows Ctrl+K on Windows/Linux, ⌘K on Mac
- Add icon-only search button in topbar for mobile viewports
- Lock html/body overflow and use 100dvh to prevent topbar scrolling off-screen on mobile

src/components/topbar-search.tsx

@@ -3,25 +3,45 @@
 import { useQuickAdd } from "@/components/quick-add-provider";
 import { NavIcon } from "@/components/nav-icon";
 
+function useShortcutLabel() {
+  if (typeof navigator === "undefined") return "⌘K";
+  return /Mac|iPhone|iPad|iPod/.test(navigator.platform) ? "⌘K" : "Ctrl+K";
+}
+
 export function TopbarSearch() {
   const { openPalette } = useQuickAdd();
+  const shortcut = useShortcutLabel();
 
   return (
-    <button
-      type="button"
-      onClick={openPalette}
-      aria-label="Search (⌘K)"
-      className="hidden md:flex items-center gap-2 h-8 px-2.5 rounded-md text-[13px]"
-      style={{
-        border: "0.5px solid var(--hair-2)",
-        background: "var(--card)",
-        color: "var(--ink-mute)",
-        width: 220,
-      }}
-    >
-      <NavIcon name="search" className="size-3.5" />
-      <span style={{ flex: 1, textAlign: "left" }}>Search…</span>
-      <span className="kbd">⌘K</span>
-    </button>
+    <>
+      {/* Desktop: pill with shortcut hint */}
+      <button
+        type="button"
+        onClick={openPalette}
+        aria-label={`Search (${shortcut})`}
+        className="hidden md:flex items-center gap-2 h-8 px-2.5 rounded-md text-[13px]"
+        style={{
+          border: "0.5px solid var(--hair-2)",
+          background: "var(--card)",
+          color: "var(--ink-mute)",
+          width: 220,
+        }}
+      >
+        <NavIcon name="search" className="size-3.5" />
+        <span style={{ flex: 1, textAlign: "left" }}>Search…</span>
+        <span className="kbd">{shortcut}</span>
+      </button>
+
+      {/* Mobile: icon-only */}
+      <button
+        type="button"
+        onClick={openPalette}
+        aria-label="Search"
+        className="flex md:hidden items-center justify-center h-8 w-8 rounded-md"
+        style={{ color: "var(--ink-mute)" }}
+      >
+        <NavIcon name="search" className="size-4" />
+      </button>
+    </>
   );
 }