feat: redesign authenticated UI with home overview and settings hub

- Add HomePage with open sessions grid, projects overview, and session composer
- Add SettingsPage with tabs for General, SSH Keys, Tool Types, Tool Configs
- Update navigation to Home, Projects, Settings
- Redirect legacy routes (/sessions, /ssh-keys, /tool-types, /tool-configs)
- Apply Inter font and warm editorial styling
- Update tests for new dashboard and projects pages

Quality gates: typecheck pass, lint pass, 15/15 tests pass

Refs: openspec/changes/ui-redesign-home-settings

apps/web/src/pages/ssh-keys.tsx

@@ -1,8 +1,10 @@
 import { useEffect, useState } from "react";
+import { useNavigate } from "react-router-dom";
 import { createSSHKey, deleteSSHKey, listSSHKeys, type SSHKey } from "../api/ssh_keys";
 import { Icon } from "../components/icon";
 
 export const SSHKeysPage = () => {
+  const navigate = useNavigate();
   const [keys, setKeys] = useState<SSHKey[]>([]);
   const [loading, setLoading] = useState(true);
   const [error, setError] = useState<string | null>(null);
@@ -61,7 +63,15 @@ export const SSHKeysPage = () => {
 
   return (
     <section className="stack">
-      <h1>SSH Keys</h1>
+      <div className="page-header">
+        <div>
+          <p className="eyebrow">Settings</p>
+          <h1>SSH Keys</h1>
+        </div>
+        <button className="secondary-button" type="button" onClick={() => navigate("/settings")}>
+          Back to settings
+        </button>
+      </div>
 
       {error && <div className="error">{error}</div>}