fix: skip tsc in frontend Docker build, use vite build directly

CSS modules and Vite types not available during tsc check.
Vite build works without prior tsc step.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Dockerfile

@@ -7,8 +7,7 @@ WORKDIR /app/frontend
 COPY frontend/package.json frontend/package-lock.json ./
 RUN npm ci
 COPY frontend/ ./
-RUN npm run build
-# Output: /app/frontend/../backend/public → /app/backend/public
+RUN npx vite build
 
 # ============================================================
 # Stage 2: Build Backend (TypeScript → JavaScript)