feat(onboarding): first-run screen offers import-existing-account and external-signer paths

- Home first-run now has three entry points: create a new profile, I already
  have an account (opens ImportProfileModal), and Sign in with a signer
  (navigates to Signer Mode where Amber/NIP-46 pairing lives).
- Copy states the per-mode truth: local-vault keys vs remote signer where the
  private key never lives on this device.
- Tests updated to assert all three entry points; 116 frontend tests green.

frontend/src/App.tsx

@@ -14,6 +14,7 @@ import { SignerScreen } from './screens/SignerScreen';
 import { SignerModeScreen } from './screens/SignerModeScreen';
 import { SettingsScreen } from './screens/SettingsScreen';
 import { CreateProfileModal } from './screens/CreateProfileModal';
+import { ImportProfileModal } from './screens/ImportProfileModal';
 import { AppProvider, useApp, useThemeSync } from './state/AppProvider';
 import type { Screen } from './lib/navigation';
 
@@ -21,6 +22,7 @@ function Shell() {
   const { state, loading, bootstrapError } = useApp();
   const [screen, setScreen] = useState<Screen>('home');
   const [createOpen, setCreateOpen] = useState(false);
+  const [importOpen, setImportOpen] = useState(false);
   const [unlockOpen, setUnlockOpen] = useState(false);
 
   useThemeSync(state?.settings.theme);
@@ -68,7 +70,11 @@ function Shell() {
           </div>
         )}
         {screen === 'home' && (
-          <HomeScreen onNavigate={setScreen} onCreateProfile={() => setCreateOpen(true)} />
+          <HomeScreen
+            onNavigate={setScreen}
+            onCreateProfile={() => setCreateOpen(true)}
+            onImportProfile={() => setImportOpen(true)}
+          />
         )}
         {screen === 'feed' && <FeedScreen onNavigate={setScreen} />}
         {screen === 'profiles' && <ProfilesScreen onCreateProfile={() => setCreateOpen(true)} />}
@@ -79,6 +85,7 @@ function Shell() {
         {screen === 'settings' && <SettingsScreen />}
       </main>
       <CreateProfileModal open={createOpen} onClose={() => setCreateOpen(false)} />
+      <ImportProfileModal open={importOpen} onClose={() => setImportOpen(false)} />
       <UnlockModal open={unlockOpen} onClose={() => setUnlockOpen(false)} />
     </div>
   );

frontend/src/screens/HomeScreen.tsx

@@ -15,9 +15,10 @@ import { useApp } from '../state/AppProvider';
 interface HomeScreenProps {
   onNavigate: (screen: Screen) => void;
   onCreateProfile: () => void;
+  onImportProfile: () => void;
 }
 
-export function HomeScreen({ onNavigate, onCreateProfile }: HomeScreenProps) {
+export function HomeScreen({ onNavigate, onCreateProfile, onImportProfile }: HomeScreenProps) {
   const { state, selectProfile } = useApp();
   const { publications, fullyPublished, loading, error } = useProfilePublications();
   const [selecting, setSelecting] = useState<string | null>(null);
@@ -43,16 +44,27 @@ export function HomeScreen({ onNavigate, onCreateProfile }: HomeScreenProps) {
             title="Welcome to Keynctr"
             description={
               <span>
-                You haven't created a profile yet. A Nostr profile is your identity on the public
+                A Nostr profile is your identity on the public Nostr network — a <code>npub</code>{' '}
-                Nostr network — a <code>npub</code> address you can share, plus a private key kept
+                address you can share. You can create a new one here (its private key is generated
-                safely on this computer. Create your first profile to start publishing notes.
+                and kept in this computer&rsquo;s encrypted vault), import an account you already
+                have, or connect an external signer like Amber so the private key never lives on
+                this device.
               </span>
             }
             action={
+              <div className="onboarding-actions">
                 <Button variant="primary" onClick={onCreateProfile}>
                   <Icon name="plus" size={18} />
-                Create your first profile
+                  Create a new profile
                 </Button>
+                <Button variant="secondary" onClick={onImportProfile}>
+                  <Icon name="key" size={18} />I already have an account
+                </Button>
+                <Button variant="ghost" onClick={() => onNavigate('signer-mode')}>
+                  <Icon name="server" size={18} />
+                  Sign in with a signer (Amber, NIP-46)
+                </Button>
+              </div>
             }
           />
           <FirstRunGuide />

frontend/src/styles.css

@@ -1402,6 +1402,18 @@ select {
   margin-top: 8px;
 }
 
+.onboarding-actions {
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  gap: 10px;
+}
+
+.onboarding-actions .btn {
+  min-width: 260px;
+  justify-content: center;
+}
+
 /* -------------------------------------------------------------------------
    Home
    ------------------------------------------------------------------------- */

frontend/src/test/App.test.tsx

@@ -16,10 +16,12 @@ describe('App', () => {
     render(<App />);
 
     expect(await screen.findByText('Welcome to Keynctr')).toBeInTheDocument();
-    expect(screen.getByRole('button', { name: /Create your first profile/i })).toBeInTheDocument();
+    expect(screen.getByRole('button', { name: /Create a new profile/i })).toBeInTheDocument();
+    expect(screen.getByRole('button', { name: /I already have an account/i })).toBeInTheDocument();
+    expect(screen.getByRole('button', { name: /Sign in with a signer/i })).toBeInTheDocument();
     expect(screen.getByText(/A Nostr profile is your identity/i)).toBeInTheDocument();
 
-    await user.click(screen.getByRole('button', { name: /Create your first profile/i }));
+    await user.click(screen.getByRole('button', { name: /Create a new profile/i }));
     expect(
       await screen.findByRole('dialog', { name: 'Create a Nostr profile' }),
     ).toBeInTheDocument();

frontend/src/test/HomeScreen.test.tsx

@@ -7,13 +7,18 @@ import { createFakeBackend, installFakeBackend } from './fakeBackend';
 
 function renderHome(
   backend: ReturnType<typeof createFakeBackend>,
-  overrides: { onNavigate?: () => void; onCreateProfile?: () => void } = {},
+  overrides: {
+    onNavigate?: () => void;
+    onCreateProfile?: () => void;
+    onImportProfile?: () => void;
+  } = {},
 ) {
   installFakeBackend(backend);
   return {
     user: userEvent.setup(),
     onNavigate: overrides.onNavigate ?? vi.fn(),
     onCreateProfile: overrides.onCreateProfile ?? vi.fn(),
+    onImportProfile: overrides.onImportProfile ?? vi.fn(),
   };
 }
 
@@ -21,7 +26,9 @@ describe('HomeScreen', () => {
   it('shows the active profile, a shortened npub, and a compose button', async () => {
     const backend = createFakeBackend();
     const { onNavigate } = renderHome(backend);
-    renderWithApp(<HomeScreen onNavigate={onNavigate} onCreateProfile={vi.fn()} />);
+    renderWithApp(
+      <HomeScreen onNavigate={onNavigate} onCreateProfile={vi.fn()} onImportProfile={vi.fn()} />,
+    );
 
     // The active profile appears in the profile list with its shortened npub.
     const profileList = await screen.findByRole('listbox');
@@ -36,7 +43,9 @@ describe('HomeScreen', () => {
   it('copies the complete npub when the copy button is clicked', async () => {
     const backend = createFakeBackend();
     renderHome(backend);
-    renderWithApp(<HomeScreen onNavigate={vi.fn()} onCreateProfile={vi.fn()} />);
+    renderWithApp(
+      <HomeScreen onNavigate={vi.fn()} onCreateProfile={vi.fn()} onImportProfile={vi.fn()} />,
+    );
 
     // The active profile row carries the "Selected" badge; find Alice via the profile list.
     const profileList = await screen.findByRole('listbox');
@@ -51,20 +60,32 @@ describe('HomeScreen', () => {
 
   it('shows the first-run state and guides the user to create a profile', async () => {
     const backend = createFakeBackend(makeEmptyState());
-    const { onCreateProfile } = renderHome(backend);
+    const { onCreateProfile, onImportProfile } = renderHome(backend);
-    renderWithApp(<HomeScreen onNavigate={vi.fn()} onCreateProfile={onCreateProfile} />);
+    renderWithApp(
+      <HomeScreen
+        onNavigate={vi.fn()}
+        onCreateProfile={onCreateProfile}
+        onImportProfile={onImportProfile}
+      />,
+    );
 
     expect(await screen.findByText('Welcome to Keynctr')).toBeInTheDocument();
+    expect(screen.getByRole('button', { name: /I already have an account/i })).toBeInTheDocument();
+    expect(screen.getByRole('button', { name: /Sign in with a signer/i })).toBeInTheDocument();
+    await userEvent.setup().click(screen.getByRole('button', { name: /Create a new profile/i }));
+    expect(onCreateProfile).toHaveBeenCalled();
     await userEvent
       .setup()
-      .click(screen.getByRole('button', { name: /Create your first profile/i }));
+      .click(screen.getByRole('button', { name: /I already have an account/i }));
-    expect(onCreateProfile).toHaveBeenCalled();
+    expect(onImportProfile).toHaveBeenCalled();
   });
 
   it('selects a profile when its row is clicked (not just the Select button)', async () => {
     const backend = createFakeBackend();
     renderHome(backend);
-    renderWithApp(<HomeScreen onNavigate={vi.fn()} onCreateProfile={vi.fn()} />);
+    renderWithApp(
+      <HomeScreen onNavigate={vi.fn()} onCreateProfile={vi.fn()} onImportProfile={vi.fn()} />,
+    );
 
     const bobRow = (await screen.findByText('Bob')).closest('.home-profile-row') as HTMLElement;
     // Clicking the name (not the Select button) should select the profile.

frontend/src/test/publications.test.tsx

@@ -23,7 +23,9 @@ function makeItem(overrides: Partial<FeedItem> & { id: string; relays: string[]
 
 function renderHome(backend: ReturnType<typeof createFakeBackend>) {
   installFakeBackend(backend);
-  renderWithApp(<HomeScreen onNavigate={vi.fn()} onCreateProfile={vi.fn()} />);
+  renderWithApp(
+    <HomeScreen onNavigate={vi.fn()} onCreateProfile={vi.fn()} onImportProfile={vi.fn()} />,
+  );
 }
 
 async function waitForData() {