Fix production build error with proper vendor chunk splitting

- Configure Vite to split vendor chunks (React, DOMPurify, video libs, Supabase)
- Add manual chunk configuration to prevent duplicate module bundling
- Clean Docker build cache and node_modules cache during build
- Update Dockerfile to force clean rebuilds

This should resolve the 'Identifier already declared' error in production
caused by DOMPurify's @xmldom dependency being bundled multiple times.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Dockerfile

@@ -7,14 +7,14 @@ WORKDIR /app
 # Copy package files
 COPY package*.json ./
 
-# Install dependencies
-RUN npm ci
+# Install dependencies with clean install
+RUN npm ci --prefer-offline --no-audit --force
 
 # Copy source code
 COPY . .
 
-# Build the application
-RUN npm run build
+# Clean any previous build artifacts and node_modules cache, then build
+RUN rm -rf dist node_modules/.cache && npm run build
 
 # Production stage - Use a simple server that works with Coolify
 FROM node:18-alpine AS production