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>

src/lib/cycle.test.ts

@@ -0,0 +1,62 @@
+// ABOUTME: Unit tests for cycle phase calculation utilities.
+// ABOUTME: Tests getCycleDay, getPhase, and phase limit functions.
+import { describe, expect, it } from "vitest";
+
+import { getCycleDay, getPhase, getPhaseLimit } from "./cycle";
+
+describe("getCycleDay", () => {
+  it("returns 1 on the first day of the cycle", () => {
+    const lastPeriod = new Date("2025-01-01");
+    const currentDate = new Date("2025-01-01");
+    expect(getCycleDay(lastPeriod, 31, currentDate)).toBe(1);
+  });
+
+  it("returns correct day within cycle", () => {
+    const lastPeriod = new Date("2025-01-01");
+    const currentDate = new Date("2025-01-15");
+    expect(getCycleDay(lastPeriod, 31, currentDate)).toBe(15);
+  });
+
+  it("wraps around after cycle length", () => {
+    const lastPeriod = new Date("2025-01-01");
+    const currentDate = new Date("2025-02-01"); // 31 days later
+    expect(getCycleDay(lastPeriod, 31, currentDate)).toBe(1);
+  });
+});
+
+describe("getPhase", () => {
+  it("returns MENSTRUAL for days 1-3", () => {
+    expect(getPhase(1)).toBe("MENSTRUAL");
+    expect(getPhase(3)).toBe("MENSTRUAL");
+  });
+
+  it("returns FOLLICULAR for days 4-14", () => {
+    expect(getPhase(4)).toBe("FOLLICULAR");
+    expect(getPhase(14)).toBe("FOLLICULAR");
+  });
+
+  it("returns OVULATION for days 15-16", () => {
+    expect(getPhase(15)).toBe("OVULATION");
+    expect(getPhase(16)).toBe("OVULATION");
+  });
+
+  it("returns EARLY_LUTEAL for days 17-24", () => {
+    expect(getPhase(17)).toBe("EARLY_LUTEAL");
+    expect(getPhase(24)).toBe("EARLY_LUTEAL");
+  });
+
+  it("returns LATE_LUTEAL for days 25-31", () => {
+    expect(getPhase(25)).toBe("LATE_LUTEAL");
+    expect(getPhase(31)).toBe("LATE_LUTEAL");
+  });
+});
+
+describe("getPhaseLimit", () => {
+  it("returns correct weekly limits for each phase", () => {
+    expect(getPhaseLimit("MENSTRUAL")).toBe(30);
+    expect(getPhaseLimit("FOLLICULAR")).toBe(120);
+    expect(getPhaseLimit("OVULATION")).toBe(80);
+    expect(getPhaseLimit("EARLY_LUTEAL")).toBe(100);
+    expect(getPhaseLimit("LATE_LUTEAL")).toBe(50);
+  });
+});