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>

e2e/screenshots.sh

@@ -0,0 +1,20 @@
+#!/usr/bin/env bash
+# Builds MindSift, starts it in demo mode with a fresh database and renews the README screenshots
+# in screenshots/. Requires podman (or docker via ENGINE=docker). Usage: e2e/screenshots.sh
+set -euo pipefail
+ENGINE="${ENGINE:-podman}"
+ROOT="$(cd "$(dirname "$0")/.." && pwd)"
+WORK="$(mktemp -d)"
+trap '"$ENGINE" rm -f mindsift-shots >/dev/null 2>&1 || true; rm -rf "$WORK"' EXIT
+
+echo "Baue Image …"
+# Version in the header, e.g. APP_VERSION=v0.2 e2e/screenshots.sh
+"$ENGINE" build -q --build-arg APP_VERSION="${APP_VERSION:-}" -t mindsift-e2e-image "$ROOT" >/dev/null
+"$ENGINE" run -d --name mindsift-shots --network host -e PORT=18081 -e MINDA_DEMO=true \
+  -e JWT_SECRET=screenshots-only-secret -v "$WORK":/data:Z mindsift-e2e-image >/dev/null
+for _ in $(seq 1 60); do curl -s -m 1 http://localhost:18081/api/v1/health >/dev/null && break; sleep 0.5; done
+
+echo "Erstelle Screenshots …"
+"$ENGINE" run --rm --network host -e MINDSIFT_URL=http://localhost:18081 -e SHOTS_DIR=/shots -e LANG=de_DE.UTF-8 \
+  -v "$ROOT/e2e":/e2e:Z -v "$ROOT/screenshots":/shots:Z -w /e2e mcr.microsoft.com/playwright:v1.48.2-jammy \
+  sh -c 'apt-get update -qq >/dev/null && apt-get install -y -qq fonts-inter >/dev/null 2>&1; npm install --no-audit --no-fund >/dev/null 2>&1 && node screenshots.mjs'