release: v0.2 – collaboration docs, richer demo data, new screenshots

- Turn the collaboration plan into module docs (Doku/modules/collaboration.md)
  describing the implemented state; remove Doku/plans
- Header version comes from the build: git tag via APP_VERSION (CI passes
  it for tag builds), otherwise "<package version>-dev"; package 0.2.0
- Sample data (setup option and demo mode): six inbox thoughts, two task
  lists with Kanban states, subtasks and due dates, shopping and packing
  lists, three notes in folders incl. a long nested outline; demo mode
  shares the note and two lists with user/user
- e2e/screenshots.sh renews the README screenshots from demo data
- README: live collaboration, editor sharing, image tags, version badge

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

frontend/src/App.tsx

@@ -52,6 +52,7 @@ import { GroupsView } from './features/teams/GroupsView';
 import { useMobileActions } from './context/MobileActionContext';
 import { MobileHeaderMenu } from './components/MobileHeaderMenu';
 import { UserAvatar } from './components/UserAvatar';
+import { APP_VERSION } from './version';
 
 type ActiveTab =
   | 'triage'
@@ -648,7 +649,7 @@ export const App: React.FC = () => {
                 <span className="font-bold text-base text-main tracking-tight leading-none">
                   {authStatus.instanceName || 'MindSift'}
                 </span>
-                <span className="text-[9px] text-muted font-mono leading-tight mt-0.5">v0.1</span>
+                <span className="text-[9px] text-muted font-mono leading-tight mt-0.5">{APP_VERSION}</span>
               </div>
               <span className="text-[11px] font-semibold text-accent bg-accent/15 px-1.5 py-0.5 rounded-md">
                 {activeTabLabelMap[activeTab]}
@@ -713,7 +714,7 @@ export const App: React.FC = () => {
               <span className="font-bold text-sm sm:text-base text-main tracking-tight leading-none">
                 {authStatus.instanceName || 'MindSift'}
               </span>
-              <span className="text-[10px] text-muted font-mono leading-tight mt-0.5">v0.1</span>
+              <span className="text-[10px] text-muted font-mono leading-tight mt-0.5">{APP_VERSION}</span>
             </div>
           </div>