Add help modal, changelog, map visits, Dockerfile, CI

- Help modal (? button or keyboard shortcut): how-to-play in Swedish,
  flavor text, full changelog sourced from src/data/version.ts
- src/data/version.ts: versioned changelog entries, in-universe Malmö voice
- Map zone clicks: each location on the Leaflet map is now clickable.
  Unlocked cult areas give resources + log entries. Locked locations show
  lore hints. 30s cooldown per location so it's a decision, not a spam button.
- Dockerfile + nginx.conf + docker-compose.yml (port 5684)
- Gitea CI workflow (identical to 2048 — derives image from repo path, needs
  TKNTKN secret, pushes :latest and :sha tags)
- README.md with mechanics summary and docker instructions

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.gitea/workflows/build.yml

@@ -0,0 +1,57 @@
+name: Docker
+
+on:
+  push:
+    branches: [main]
+  workflow_dispatch:
+
+jobs:
+  build-and-push:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Derive image name and tags
+        id: meta
+        shell: bash
+        run: |
+          set -euo pipefail
+
+          SERVER_URL="${GITHUB_SERVER_URL:-${GITEA_SERVER_URL:-}}"
+          REPO="${GITHUB_REPOSITORY:-${GITEA_REPOSITORY:-}}"
+          SHA="${GITHUB_SHA:-${GITEA_SHA:-}}"
+
+          if [[ -z "${SERVER_URL}" || -z "${REPO}" || -z "${SHA}" ]]; then
+            echo "Missing SERVER_URL/REPO/SHA env vars." >&2
+            echo "SERVER_URL='${SERVER_URL}' REPO='${REPO}' SHA='${SHA}'" >&2
+            exit 1
+          fi
+
+          HOST=$(echo "${SERVER_URL}" | sed 's|https://||;s|http://||')
+          IMAGE=$(echo "${HOST}/${REPO}" | tr '[:upper:]' '[:lower:]')
+          SHORT_SHA=$(echo "${SHA}" | cut -c1-7)
+
+          echo "host=${HOST}" >> "$GITHUB_OUTPUT"
+          echo "image=${IMAGE}" >> "$GITHUB_OUTPUT"
+          echo "short_sha=${SHORT_SHA}" >> "$GITHUB_OUTPUT"
+
+      - name: Log in to Gitea container registry
+        uses: docker/login-action@v3
+        with:
+          registry: ${{ steps.meta.outputs.host }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.TKNTKN }}
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Build and push
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          file: Dockerfile
+          push: true
+          tags: |
+            ${{ steps.meta.outputs.image }}:latest
+            ${{ steps.meta.outputs.image }}:${{ steps.meta.outputs.short_sha }}