feat: initial brainstorming app — Nuxt 3 + SQLite + admin auth

Nuxt 3 app with:
- SQLite (better-sqlite3) for persistence
- Anonymous idea submission and voting
- Admin auth with session cookies
- AI analysis via Gemini API
- Nuxt UI components + Tailwind

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

server/api/auth/login.post.ts

@@ -0,0 +1,17 @@
+import { checkPassword, createSession } from '../../utils/auth'
+
+export default defineEventHandler(async (event) => {
+  const { password } = await readBody(event)
+  if (!password || !checkPassword(password)) {
+    throw createError({ statusCode: 401, statusMessage: 'Invalid password' })
+  }
+  const token = createSession()
+  setCookie(event, 'session', token, {
+    httpOnly: true,
+    secure: true,
+    sameSite: 'strict',
+    maxAge: 86400,
+    path: '/',
+  })
+  return { ok: true }
+})