feat: implement SSH key management

- Add backend API endpoints for SSH key CRUD (POST, GET, DELETE)
- Implement Ed25519 key generation with Fernet-encrypted private keys
- Add frontend SSH keys page with generate, list, and delete functionality
- Include copy-to-clipboard for public keys
- Add responsive CSS styles for key cards
- Register ssh_keys router in main.py
- Add basic auth tests for SSH key endpoints

Quality gates: ruff ✓, mypy ✓, typecheck ✓, lint ✓

apps/web/src/router.tsx

@@ -6,6 +6,7 @@ import { DashboardPage } from "./pages/dashboard";
 import { LoginRedirectPage, NotFoundPage, PlaceholderPage } from "./pages/placeholder";
 import { ProfilePage } from "./pages/profile";
 import { ProjectsPage } from "./pages/projects";
+import { SSHKeysPage } from "./pages/ssh-keys";
 
 export const AppRouter = () => {
   return (
@@ -22,7 +23,7 @@ export const AppRouter = () => {
         <Route index element={<DashboardPage />} />
         <Route path="projects" element={<ProjectsPage />} />
         <Route path="repositories" element={<PlaceholderPage title="Repositories" />} />
-        <Route path="ssh-keys" element={<PlaceholderPage title="SSH Keys" />} />
+        <Route path="ssh-keys" element={<SSHKeysPage />} />
         <Route path="profile" element={<ProfilePage />} />
         <Route path="settings" element={<PlaceholderPage title="Settings" />} />
       </Route>