fix vite web build to work with subpath

Dockerfile

@@ -2,6 +2,11 @@
 FROM node:23-alpine as builder
 WORKDIR /app
 
+# PUBLIC_PATH at build time: passed as VITE_BASE_PATH so assets are built for that subpath.
+# Use "/" for root or "/feishin/" for a subpath (trailing slash required for subpaths).
+ARG PUBLIC_PATH=/
+ENV PUBLIC_PATH=${PUBLIC_PATH}
+
 # Copy package.json first to cache node_modules
 COPY package.json pnpm-lock.yaml .
 
@@ -10,18 +15,24 @@ RUN npm install -g pnpm
 RUN pnpm install
 
 # Copy code and build with cached modules
+# Normalize PUBLIC_PATH to trailing slash for subpaths (Vite base expects "/" or "/foo/")
 COPY . .
-RUN pnpm run build:web
+RUN VITE_BASE_PATH=$(echo "$PUBLIC_PATH" | sed 's|/*$|/|') && \
+    export VITE_BASE_PATH && \
+    pnpm run build:web
 
 # --- Production stage
 FROM nginx:alpine-slim
 
+ARG PUBLIC_PATH=/
+ENV PUBLIC_PATH=${PUBLIC_PATH}
+
 COPY --chown=nginx:nginx --from=builder /app/out/web /usr/share/nginx/html
 COPY ./settings.js.template /etc/nginx/templates/settings.js.template
 COPY ng.conf.template /etc/nginx/templates/default.conf.template
 
 ENV SERVER_LOCK=false SERVER_NAME="" SERVER_TYPE="" SERVER_URL=""
-ENV LEGACY_AUTHENTICATION="" ANALYTICS_DISABLED="" PUBLIC_PATH="/"
+ENV LEGACY_AUTHENTICATION="" ANALYTICS_DISABLED=""
 
 EXPOSE 9180
 CMD ["nginx", "-g", "daemon off;"]