feat: remove AI extensions, restructure settings, and add atomic voucher commits (#157)

Remove AI-dependent extensions (ai-chat, ai-categorization, receipt-ocr,
invoice-inbox) and their infrastructure (lib/ai/*, ai-consent, LangChain/
Anthropic/OpenAI deps) to simplify core and reduce bundle size.

Restructure monolithic settings page into dedicated sub-pages (company,
bookkeeping, invoicing, tax, banking, api, account, team, templates) with
shared layout and sidebar navigation.

Add atomic commit_journal_entry RPC so voucher number increment and status
update happen in a single transaction — prevents burned numbers on constraint
failures. Add continuity check report and voucher gap explanation tracking.

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

components/dashboard/DashboardContent.tsx

@@ -217,7 +217,7 @@ export default function DashboardContent({ firstName, settings, summary, onboard
   if (summary.expiringBankConnections && summary.expiringBankConnections.length > 0) {
     const conn = summary.expiringBankConnections[0]
     alertItems.push(
-      <Link key="bank-expiry" href="/settings?tab=banking" className="group">
+      <Link key="bank-expiry" href="/settings/banking" className="group">
         <Card className="h-full border-warning/30 hover:bg-warning/[0.03] transition-colors">
           <CardContent className="p-4">
             <div className="flex items-center gap-3">