fix(frontend): remove duplicate Dashboard entry in nav rail

The sidebar rendered /dashboard twice: once as a hardcoded NavItem
(lines 45-50) and again via navItems.map() (navItems[0] is also
/dashboard). Dropped the hardcoded item so the single source of truth
(navItems in lib/navigation.ts) drives the rail. Removed the now-unused
LayoutDashboard import.

tsc + biome green.

Co-Authored-By: Claude Opus 5 (Nous Research)

services/frontend/src/components/shell/nav-rail.tsx

@@ -1,6 +1,5 @@
 "use client";
 
-import { LayoutDashboard } from "lucide-react";
 import { usePathname } from "next/navigation";
 import { isActivePath, navItems } from "@/lib/navigation";
 import { cn } from "@/lib/utils";
@@ -42,12 +41,6 @@ export function NavRail() {
 
   return (
     <nav className="glass m-3 mr-0 flex w-[68px] flex-col items-center gap-1 rounded-[18px] py-4">
-      <NavItem
-        href="/dashboard"
-        label="Dashboard"
-        active={isActivePath(path, "/dashboard")}
-        Icon={LayoutDashboard}
-      />
       <div className="flex flex-1 flex-col gap-1">
         {navItems.map((item) => (
           <NavItem