Fix Docker build: copy .npmrc + use --legacy-peer-deps for npm ci

vite-plugin-pwa peer-depends on vite <=5 but project uses vite 7 (works fine);
npm ci needs legacy-peer-deps which lives in .npmrc (now copied before install).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.npmrc

@@ -1,2 +1 @@
 legacy-peer-deps=true
-npm audit --omit=dev

Dockerfile

@@ -11,8 +11,8 @@ RUN apt-get update && apt-get install -y --no-install-recommends ca-certificates
     && rm -rf /var/lib/apt/lists/*
 
 # Install dependencies (full install — tsx/vite are needed for build & runtime)
-COPY package.json package-lock.json ./
+COPY package.json package-lock.json .npmrc ./
-RUN npm ci
+RUN npm ci --legacy-peer-deps
 
 # Copy source and build the frontend
 COPY . .