Add Phase 0: sign-up, login, and profile

- Next.js (App Router) + TypeScript + Tailwind
- Prisma + SQLite for the User model
- Sign-up with 18+ age gate, email/password validation (zod), bcrypt hashing
- Login via NextAuth credentials provider, JWT sessions
- Protected /profile route (view + edit name/bio)

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VL5YUEf2B9LG4xdVUQwcSg

prisma/migrations/20260924134740_init/migration.sql

@@ -0,0 +1,14 @@
+-- CreateTable
+CREATE TABLE "User" (
+    "id" TEXT NOT NULL PRIMARY KEY,
+    "email" TEXT NOT NULL,
+    "passwordHash" TEXT NOT NULL,
+    "name" TEXT NOT NULL,
+    "age" INTEGER NOT NULL,
+    "bio" TEXT NOT NULL DEFAULT '',
+    "createdAt" DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "updatedAt" DATETIME NOT NULL
+);
+
+-- CreateIndex
+CREATE UNIQUE INDEX "User_email_key" ON "User"("email");