feat: organizations decide who sees whom; sharing only by owners

- Server admins manage organizations (one per user); new admin section,
  organization on user creation and invites, setup creates the first one
- Sharing modes private / organizations / open, enforced centrally
  (CanSee, CanShareWith) for directory, all shares and groups; unknown and
  invisible targets give the same error
- Losing visibility (org change, mode change, leaving a group) prunes shares,
  group memberships and task assignments; dry run warns before tightening
- Only owners share; editors can no longer reshare lists or remove others'
  shares; legacy task_lists.team_id and old /organizations endpoints removed
  (FLAW-06, FLAW-10, FLAW-24)
- Schema version: outdated databases are wiped and recreated on start
- Fix setup sample data (createSampleData was ignored); setup and admin
  use a shared ToggleSwitch instead of checkboxes
- Docs: sharing-and-permissions rewritten, ui-patterns, REST, DB, flaws

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

frontend/src/features/auth/SetupAndAuthView.tsx

@@ -11,8 +11,9 @@ import {
   Check,
   AlertCircle,
 } from 'lucide-react';
-import { AuthStatus, User } from '../../lib/types';
+import { AuthStatus, SharingMode, User } from '../../lib/types';
 import { api, triggerHaptic } from '../../lib/api';
+import { ToggleSwitch } from '../../components/ToggleSwitch';
 
 interface SetupAndAuthViewProps {
   authStatus: AuthStatus;
@@ -29,9 +30,7 @@ export const SetupAndAuthView: React.FC<SetupAndAuthViewProps> = ({
   const [setupPassword, setSetupPassword] = useState('');
   const [setupPasswordConfirm, setSetupPasswordConfirm] = useState('');
   const [instanceName, setInstanceName] = useState(authStatus.instanceName || 'MindSift');
-  const [sharingMode, setSharingMode] = useState<'open' | 'teams_only' | 'strict_private'>(
-    'teams_only'
-  );
+  const [sharingMode, setSharingMode] = useState<SharingMode>('organizations');
   const [allowRegistration, setAllowRegistration] = useState(false);
   const [createSampleData, setCreateSampleData] = useState(false);
 
@@ -241,31 +240,31 @@ export const SetupAndAuthView: React.FC<SetupAndAuthViewProps> = ({
                 <div className="grid grid-cols-1 sm:grid-cols-3 gap-2">
                   <button
                     type="button"
-                    onClick={() => setSharingMode('strict_private')}
+                    onClick={() => setSharingMode('private')}
                     className={`p-2.5 text-left border transition-colors ${
-                      sharingMode === 'strict_private'
+                      sharingMode === 'private'
                         ? 'bg-panel border-accent text-main'
                         : 'border-border text-muted hover:text-main'
                     }`}
                   >
-                    <p className="font-bold text-xs">Strikt Privat</p>
+                    <p className="font-bold text-xs">Privat</p>
                     <p className="text-[10px] text-muted mt-0.5">
-                      Keiner sieht andere Nutzer. Komplett isoliert.
+                      Keiner sieht andere Nutzer. Teilen und Gruppen sind aus.
                     </p>
                   </button>
 
                   <button
                     type="button"
-                    onClick={() => setSharingMode('teams_only')}
+                    onClick={() => setSharingMode('organizations')}
                     className={`p-2.5 text-left border transition-colors ${
-                      sharingMode === 'teams_only'
+                      sharingMode === 'organizations'
                         ? 'bg-panel border-accent text-main'
                         : 'border-border text-muted hover:text-main'
                     }`}
                   >
-                    <p className="font-bold text-xs">Teams isoliert</p>
+                    <p className="font-bold text-xs">Organisationen</p>
                     <p className="text-[10px] text-muted mt-0.5">
-                      Nutzer sehen nur Mitglieder ihrer eigenen Teams.
+                      Nutzer sehen nur Mitglieder ihrer Organisation. Du startest in einer Organisation mit dem Namen der Instanz.
                     </p>
                   </button>
 
@@ -287,7 +286,7 @@ export const SetupAndAuthView: React.FC<SetupAndAuthViewProps> = ({
               </div>
 
               <div className="pt-2 border-t border-border space-y-2">
-                <label className="flex items-center justify-between cursor-pointer select-none">
+                <div className="flex items-center justify-between gap-3 select-none">
                   <div>
                     <span className="font-medium text-main block">
                       Öffentliche Selbstregistrierung erlauben
@@ -297,30 +296,21 @@ export const SetupAndAuthView: React.FC<SetupAndAuthViewProps> = ({
                       Admin angelegt werden.
                     </span>
                   </div>
-                  <input
-                    type="checkbox"
-                    checked={allowRegistration}
-                    onChange={(e) => setAllowRegistration(e.target.checked)}
-                    className="w-4 h-4 accent-blue-600"
-                  />
-                </label>
+                  <ToggleSwitch checked={allowRegistration} onChange={setAllowRegistration} />
+                </div>
 
-                <label className="flex items-center justify-between cursor-pointer select-none pt-1">
+                <div className="flex items-center justify-between gap-3 select-none pt-1">
                   <div>
                     <span className="font-medium text-main block">
-                      Start-Beispieldaten anlegen
+                      Beispieldaten anlegen
                     </span>
                     <span className="text-[11px] text-muted">
-                      Erstellt wenige Beispiel-Gedanken und ein Einführungsdokument zum Testen.
+                      Füllt dein Konto mit Beispiel-Gedanken, Notizen, Aufgabenlisten und Einkaufslisten zum Ausprobieren.
+                      Es werden keine weiteren Benutzer angelegt.
                     </span>
                   </div>
-                  <input
-                    type="checkbox"
-                    checked={createSampleData}
-                    onChange={(e) => setCreateSampleData(e.target.checked)}
-                    className="w-4 h-4 accent-blue-600"
-                  />
-                </label>
+                  <ToggleSwitch checked={createSampleData} onChange={setCreateSampleData} />
+                </div>
               </div>
             </div>