feat: migrate schema to DATE type, add test infrastructure

- Migrate due_date/next_occurrence columns from TIMESTAMPTZ to DATE
- Update serializeRow() to distinguish DATE vs TIMESTAMPTZ serialization
- Simplify frontend date parsing (no more timezone workarounds)
- Add Vitest + Testing Library test infrastructure
- Add initial date parsing/formatting unit tests
- Update package.json with dev dependencies (vitest, testing-library, jsdom)

Dockerfile

@@ -0,0 +1,52 @@
+# Build stage
+FROM node:22-alpine AS builder
+
+WORKDIR /app
+
+# Copy package files
+COPY package.json package-lock.json ./
+
+# Install dependencies
+RUN npm ci
+
+# Copy source code
+COPY . .
+
+# Build the Next.js app
+RUN npm run build
+
+# Production stage
+FROM node:22-alpine
+
+WORKDIR /app
+
+ENV NODE_ENV=production
+ENV HOSTNAME="0.0.0.0"
+ENV PORT=3000
+
+# Install postgres client, netcat, and tsx for migrations
+RUN apk add --no-cache postgresql-client netcat-openbsd && \
+    npm install -g tsx
+
+# Create a non-root user
+RUN addgroup --system --gid 1001 nodejs && \
+    adduser --system --uid 1001 nextjs
+
+# Copy the built app from builder
+COPY --from=builder /app/public ./public
+COPY --from=builder --chown=nextjs:nodejs /app/.next/standalone/ ./
+COPY --from=builder --chown=nextjs:nodejs /app/.next/static ./.next/static
+COPY --from=builder /app/package.json ./
+
+# Copy migration script (for initial setup)
+COPY --chown=nextjs:nodejs src/server/db/migrate.ts ./migrate.ts
+
+# Create startup script
+COPY start.sh /app/start.sh
+RUN chmod +x /app/start.sh
+
+USER nextjs
+
+EXPOSE 3000
+
+CMD ["/app/start.sh"]