require auth to log in (lock screen), remove auth-on-logout, remove welcome card from multicoin dashboard, relocate login buttons to root welcome page

- login('multi') no longer silently loads seed from keychain — shows locked screen with Touch ID/password
- Removed welcome card from EvmDashboard (multicoin route), root / handles account selection
- Root welcome page buttons call w.login() before navigating to respective routes
- Monero welcome page buttons also call w.login() before navigating
- logout now simply calls w.logout() + navigate('/') with no auth required
- Removed tab-bar logout buttons; logout moved to wallet card alongside refresh/settings/stop

apps/desktop/src/routes/index.svelte

@@ -33,12 +33,12 @@
 			<CardContent>
 				<div class="flex flex-col gap-3">
 					<Button
-						onclick={() => navigate('/multicoin')}
+						onclick={async () => { await w.login('multi'); navigate('/multicoin') }}
 						class="w-full">
 						Multi Coins (ETH / BSC / Polygon)
 					</Button>
 					<Button
-						onclick={() => navigate('/monero')}
+						onclick={async () => { await w.login('monero'); navigate('/monero') }}
 						variant="outline"
 						class="w-full">
 						Monero