feat(watchlist): add tabs for Watching vs My Portfolio

- Sidebar: treat Portfolio as sub-view of WATCHLIST instead of separate nav item
- WATCHLIST header: add tab switcher (Watching ↔ My Portfolio) to match Terminal concept
- PORTFOLIO header: mirror the same tabs so users can jump back to Watchlist

frontend/src/app/terminal/portfolio/page.tsx

@@ -392,10 +392,35 @@ export default function PortfolioPage() {
                 <h1 className="text-3xl font-bold tracking-tight text-white">Portfolio</h1>
               </div>
               <p className="text-zinc-400 max-w-lg">
-                Track your domain investments, valuations, and ROI. Your personal domain asset manager.
+                Track your owned domains, valuations, and ROI. Switch back to your Watchlist anytime.
               </p>
             </div>
             
+            <div className="flex flex-col items-end gap-3">
+              {/* View Tabs: Watching vs My Portfolio */}
+              <div className="flex items-center gap-1 bg-white/5 p-1 rounded-lg">
+                <Link
+                  href="/terminal/watchlist"
+                  className={clsx(
+                    "px-3 py-1.5 rounded-md text-xs font-medium transition-all flex items-center gap-2 text-zinc-400 hover:text-zinc-200 hover:bg-white/5"
+                  )}
+                >
+                  <Eye className="w-3.5 h-3.5" />
+                  Watching
+                </Link>
+                <button
+                  type="button"
+                  className={clsx(
+                    "px-3 py-1.5 rounded-md text-xs font-medium transition-all",
+                    "flex items-center gap-2",
+                    "bg-zinc-800 text-white shadow-sm"
+                  )}
+                >
+                  <Shield className="w-3.5 h-3.5" />
+                  My Portfolio
+                </button>
+              </div>
+
               {canUsePortfolio && (
                 <button
                   onClick={() => {
@@ -408,6 +433,7 @@ export default function PortfolioPage() {
                 </button>
               )}
             </div>
+          </div>
 
           {/* Messages */}
           {error && (

frontend/src/app/terminal/watchlist/page.tsx

@@ -376,10 +376,36 @@ export default function WatchlistPage() {
                 <h1 className="text-3xl font-bold tracking-tight text-white">Watchlist</h1>
               </div>
               <p className="text-zinc-400 max-w-lg">
-                Monitor availability, health, and expiration dates for your tracked domains.
+                Monitor external domains you care about and manage your own portfolio in one place.
               </p>
             </div>
             
+            {/* Tabs + Quick Stats */}
+            <div className="flex flex-col items-end gap-3">
+              {/* View Tabs: Watching vs My Portfolio */}
+              <div className="flex items-center gap-1 bg-white/5 p-1 rounded-lg">
+                <Link
+                  href="/terminal/watchlist"
+                  className={clsx(
+                    "px-3 py-1.5 rounded-md text-xs font-medium transition-all",
+                    "flex items-center gap-2",
+                    "bg-zinc-800 text-white shadow-sm"
+                  )}
+                >
+                  <Eye className="w-3.5 h-3.5" />
+                  Watching
+                </Link>
+                <Link
+                  href="/terminal/portfolio"
+                  className={clsx(
+                    "px-3 py-1.5 rounded-md text-xs font-medium transition-all flex items-center gap-2 text-zinc-400 hover:text-zinc-200 hover:bg-white/5"
+                  )}
+                >
+                  <Shield className="w-3.5 h-3.5" />
+                  My Portfolio
+                </Link>
+              </div>
+
               {/* Quick Stats Pills */}
               <div className="flex gap-2">
                 {stats.available > 0 && (
@@ -394,6 +420,7 @@ export default function WatchlistPage() {
                 </div>
               </div>
             </div>
+          </div>
 
           {/* Metric Grid */}
           <div className="grid grid-cols-1 md:grid-cols-4 gap-4">

frontend/src/components/Sidebar.tsx

@@ -106,12 +106,6 @@ export function Sidebar({ collapsed: controlledCollapsed, onCollapsedChange }: S
       icon: Eye,
       badge: availableCount || null,
     },
-    { 
-      href: '/terminal/portfolio', 
-      label: 'PORTFOLIO', 
-      icon: Briefcase,
-      badge: null,
-    },
     { 
       href: '/terminal/listing', 
       label: 'FOR SALE',