Initial project setup for PhaseFlow

Set up Next.js 16 project with TypeScript for a training decision app
that integrates menstrual cycle phases with Garmin biometrics for
Hashimoto's thyroiditis management.

Stack: Next.js 16, React 19, Tailwind/shadcn, PocketBase, Drizzle,
Zod, Resend, Vitest, Biome, Lefthook, Nix dev environment.

Includes:
- 7 page routes (dashboard, login, settings, calendar, history, plan)
- 12 API endpoints (garmin, user, cycle, calendar, overrides, cron)
- Core lib utilities (decision engine, cycle phases, nutrition, ICS)
- Type definitions and component scaffolding
- Python script for Garmin token bootstrapping
- Initial unit tests for cycle utilities

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

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

vitest.config.ts

@@ -0,0 +1,12 @@
+// ABOUTME: Vitest configuration for unit and integration testing.
+// ABOUTME: Configures jsdom environment for React component testing.
+import react from "@vitejs/plugin-react";
+import { defineConfig } from "vitest/config";
+
+export default defineConfig({
+  plugins: [react()],
+  test: {
+    environment: "jsdom",
+    include: ["src/**/*.test.{ts,tsx}"],
+  },
+});