feat(auth): Session-Wiederherstellung nach Reload ohne vollen Login

Nach gültigem Server-Cookie wird automatisch Passkey oder PIN zum Entsperren angeboten, statt die komplette Anmelde-Maske zu zeigen.

Co-authored-by: Cursor <cursoragent@cursor.com>

client/src/services/auth.ts

@@ -64,6 +64,15 @@ export function persistSessionUserId(userId: string | undefined): void {
   }
 }
 
+/** Username to use when re-unlocking after reload (active account or sole remembered user). */
+export function resolveRestoreUsername(): string | null {
+  const stored = localStorage.getItem('active_username')
+  if (stored) return stored
+  const known = getKnownUsernames()
+  if (known.length === 1) return known[0]
+  return null
+}
+
 export async function reauthWithPasskey(): Promise<boolean> {
   const options = await apiJson<any>(`${API_BASE}/reauth-options`, {
     method: 'POST'

client/src/services/authSession.test.ts

@@ -2,6 +2,7 @@ import { beforeEach, describe, expect, it } from 'vitest'
 import {
   hasUnlockedLocalCrypto,
   hasUnlockedLocalSession,
+  resolveRestoreUsername,
   setActiveMasterKey
 } from './auth.js'
 
@@ -33,6 +34,28 @@ describe('local session unlock checks', () => {
   })
 })
 
+describe('resolveRestoreUsername', () => {
+  beforeEach(() => {
+    localStorage.clear()
+  })
+
+  it('prefers active_username from storage', () => {
+    localStorage.setItem('active_username', 'captain')
+    localStorage.setItem('daagbox_known_users', JSON.stringify(['other']))
+    expect(resolveRestoreUsername()).toBe('captain')
+  })
+
+  it('falls back to a single remembered user', () => {
+    localStorage.setItem('daagbox_known_users', JSON.stringify(['solo']))
+    expect(resolveRestoreUsername()).toBe('solo')
+  })
+
+  it('returns null when multiple users and no active username', () => {
+    localStorage.setItem('daagbox_known_users', JSON.stringify(['alpha', 'beta']))
+    expect(resolveRestoreUsername()).toBeNull()
+  })
+})
+
 describe('persistSessionUserId', () => {
   beforeEach(() => {
     localStorage.clear()