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>

Dockerfile

@@ -0,0 +1,24 @@
+# Stage 1: Build Vite SPA
+FROM node:22-alpine AS webapp-builder
+WORKDIR /webapp
+COPY webapp/package.json webapp/package-lock.json ./
+RUN npm ci
+COPY webapp/ ./
+RUN npm run build
+
+# Stage 2: Build Go server
+FROM golang:1.25-alpine AS go-builder
+WORKDIR /app
+COPY backend/go.mod backend/go.sum ./
+RUN go mod download
+COPY backend/ ./
+# Inject built SPA into embed path
+COPY --from=webapp-builder /webapp/dist ./internal/api/webapp/
+RUN CGO_ENABLED=0 GOOS=linux go build -o /server ./cmd/server
+RUN CGO_ENABLED=0 GOOS=linux go build -o /createuser ./cmd/createuser
+
+# Stage 3: Minimal runtime image
+FROM gcr.io/distroless/static-debian12
+COPY --from=go-builder /server /server
+COPY --from=go-builder /createuser /createuser
+ENTRYPOINT ["/server"]