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>

nginx.conf

@@ -0,0 +1,10 @@
+server {
+    listen 80;
+    root /usr/share/nginx/html;
+    index index.html;
+    location / {
+        try_files $uri $uri/ /index.html;
+    }
+    gzip on;
+    gzip_types text/css application/javascript application/json image/svg+xml;
+}