Add persistent navbar with SSH Keys link

Refactor App.tsx to use Layout + Outlet pattern with sticky navbar
containing: Dashboard | Machines | Sync Pairs | Jobs | SSH Keys | Settings.
Clean up redundant button row from Dashboard and inline SSH Keys links.

web/src/pages/Dashboard.tsx

@@ -1,5 +1,4 @@
 import { useEffect, useState } from 'react';
-import { Link } from 'react-router-dom';
 import { api, Machine, Job } from '../api/client';
 
 export default function Dashboard() {
@@ -66,11 +65,6 @@ export default function Dashboard() {
           </table>
         )}
       </div>
-      <div className="mt-4 flex gap-4">
-        <Link to="/machines" className="bg-blue-600 hover:bg-blue-700 text-white px-4 py-2 rounded">Machines</Link>
-        <Link to="/sync-pairs" className="bg-blue-600 hover:bg-blue-700 text-white px-4 py-2 rounded">Sync Pairs</Link>
-        <Link to="/jobs" className="bg-blue-600 hover:bg-blue-700 text-white px-4 py-2 rounded">All Jobs</Link>
-      </div>
     </div>
   );
 }

web/src/pages/Machines.tsx

@@ -1,5 +1,4 @@
 import { useEffect, useState } from 'react';
-import { Link } from 'react-router-dom';
 import { api, Machine, SSHKey } from '../api/client';
 
 export default function Machines() {
@@ -77,10 +76,7 @@ export default function Machines() {
   return (
     <div className="p-6">
       <div className="flex justify-between items-center mb-6">
-        <div className="flex items-center gap-4">
-          <h1 className="text-2xl font-bold">Machines</h1>
-          <Link to="/ssh-keys" className="text-sm text-blue-400 hover:text-blue-300">Manage SSH Keys</Link>
-        </div>
+        <h1 className="text-2xl font-bold">Machines</h1>
         <button onClick={() => setShowForm(true)} className="bg-blue-600 hover:bg-blue-700 text-white px-4 py-2 rounded">
           Add Machine
         </button>

web/src/pages/Settings.tsx

@@ -1,5 +1,4 @@
 import { useState, useEffect } from 'react';
-import { Link } from 'react-router-dom';
 
 export default function Settings() {
   const [pubKey, setPubKey] = useState('');
@@ -36,14 +35,6 @@ export default function Settings() {
         </button>
       </div>
 
-      <div className="bg-gray-800 rounded-lg p-4 mb-6">
-        <h2 className="text-lg font-semibold mb-3">SSH Keys</h2>
-        <p className="text-gray-400 text-sm mb-3">
-          Manage SSH key pairs for authenticating to remote machines. Go to the{' '}
-          <Link to="/ssh-keys" className="text-blue-400 hover:text-blue-300">SSH Keys page</Link>.
-        </p>
-      </div>
-
       <div className="bg-gray-800 rounded-lg p-4">
         <h2 className="text-lg font-semibold mb-3">Quick Reference</h2>
         <div className="text-gray-400 text-sm space-y-2">