Remove nginx/webapp container; single Go server serves SPA + API

- Add root Dockerfile: node build → copy dist into Go embed path → distroless binary
- Update docker-compose: one service (api on :9050), DB renamed ralph→pamietnik
- Remove references to RALPH/reisejournal across all docs and configs

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

webapp/nginx.conf

@@ -2,6 +2,16 @@ server {
     listen 80;
 
     # API und Auth-Endpunkte zum Backend proxieren
+    location /healthz {
+        proxy_pass http://api:8080;
+        proxy_set_header Host $host;
+    }
+
+    location /readyz {
+        proxy_pass http://api:8080;
+        proxy_set_header Host $host;
+    }
+
     location /v1/ {
         proxy_pass http://api:8080;
         proxy_set_header Host $host;