feat: implement account switcher component and state management

- Add AccountSwitcher component for managing user accounts with UI for switching, adding, and logging out.
- Create account state manager to handle snapshots of account-specific states for efficient switching.
- Introduce utility functions for account management, including ID generation and avatar color assignment.
- Implement Zustand store for account management, supporting addition, removal, and state retrieval of accounts.

locales/de/common.json

@@ -34,6 +34,9 @@
     "dismiss": "Schließen",
     "or": "oder",
     "sign_in_sso": "Mit SSO anmelden",
+    "add_account_title": "Konto hinzufügen",
+    "add_account_subtitle": "Mit einem anderen Konto anmelden",
+    "cancel": "Abbrechen",
     "website": "Webseite",
     "imprint": "Impressum",
     "privacy_policy": "Datenschutz",
@@ -58,6 +61,11 @@
     "storage_free": "Frei",
     "storage_total": "Gesamt",
     "sign_out": "Abmelden",
+    "sign_out_of": "Von {account} abmelden",
+    "sign_out_all": "Von allen Konten abmelden",
+    "add_account": "Konto hinzufügen",
+    "set_as_default": "Als Standard festlegen",
+    "switch_account": "Konto wechseln",
     "contacts": "Kontakte",
     "calendar": "Kalender",
     "settings": "Einstellungen",