Add Railway deploy files for web.yaak.app and the send proxy

Dockerfile.web

@@ -0,0 +1,20 @@
+# syntax=docker/dockerfile:1
+# web.yaak.app — the browser Yaak client, built static and served by Caddy.
+FROM node:22-slim AS build
+WORKDIR /app
+RUN apt-get update && apt-get install -y --no-install-recommends git python3 make g++ ca-certificates \
+    && rm -rf /var/lib/apt/lists/*
+COPY . .
+RUN git init -q && git add -A \
+    && git -c user.email=build@yaak.app -c user.name=build commit -qm build
+# Build-time: which send proxy the tab talks to (baked into the bundle by Vite).
+ARG VITE_YAAK_SEND_PROXY_URL
+ENV VITE_YAAK_SEND_PROXY_URL=$VITE_YAAK_SEND_PROXY_URL
+ENV YAAK_TARGET=web
+ENV SKIP_WASM_BUILD=1
+RUN npm ci
+RUN node_modules/.bin/vp -C apps/yaak-client build
+
+FROM caddy:2-alpine
+COPY deploy/web/Caddyfile /etc/caddy/Caddyfile
+COPY --from=build /app/dist/apps/yaak-client /srv