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/app/api/calendar/[userId]/[token].ics/route.ts

@@ -0,0 +1,23 @@
+// ABOUTME: API route for ICS calendar feed generation.
+// ABOUTME: Returns subscribable iCal feed with cycle phases and warnings.
+import { type NextRequest, NextResponse } from "next/server";
+
+interface RouteParams {
+  params: Promise<{
+    userId: string;
+    token: string;
+  }>;
+}
+
+export async function GET(_request: NextRequest, { params }: RouteParams) {
+  const { userId, token } = await params;
+  void token; // Token will be used for validation
+  // TODO: Implement ICS feed generation
+  // Validate token, generate ICS content, return with correct headers
+  return new NextResponse(`ICS feed for user ${userId} not implemented`, {
+    status: 501,
+    headers: {
+      "Content-Type": "text/calendar; charset=utf-8",
+    },
+  });
+}