fix: lazy DB initialization — useDb() called inside handlers, not at import

useRuntimeConfig() and better-sqlite3 were being called at module
top-level, which crashes during Nitro server startup. Now all DB
access is lazy via useDb(), and auth uses process.env directly.

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

server/api/ideas/index.post.ts

@@ -1,6 +1,7 @@
-import db from '../../utils/db'
+import { useDb } from '../../utils/db'
 
 export default defineEventHandler(async (event) => {
+  const db = useDb()
   const { text, category } = await readBody(event)
   if (!text?.trim()) {
     throw createError({ statusCode: 400, statusMessage: 'Text is required' })