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)

docker-compose.yml

@@ -0,0 +1,37 @@
+version: '3.8'
+
+services:
+  postgres:
+    image: postgres:16-alpine
+    container_name: vixtix-db
+    restart: unless-stopped
+    environment:
+      POSTGRES_USER: vixtix
+      POSTGRES_PASSWORD: vixtix_secret
+      POSTGRES_DB: vixtix
+    ports:
+      - "5433:5432"
+    volumes:
+      - vixtix-data:/var/lib/postgresql/data
+    healthcheck:
+      test: ["CMD-SHELL", "pg_isready -U vixtix"]
+      interval: 5s
+      timeout: 5s
+      retries: 5
+
+  vixtix:
+    image: vixtix:latest
+    container_name: vixtix
+    restart: unless-stopped
+    depends_on:
+      postgres:
+        condition: service_healthy
+    ports:
+      - "3070:3000"
+    environment:
+      DATABASE_URL: postgresql://vixtix:vixtix_secret@postgres:5432/vixtix
+      DB_HOST: postgres
+      DB_PORT: 5432
+
+volumes:
+  vixtix-data: