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/settings/SettingsLoadingSkeleton.tsx

@@ -0,0 +1,25 @@
+export function SettingsLoadingSkeleton() {
+  return (
+    <div className="space-y-8 animate-in fade-in duration-300">
+      {[1, 2].map(i => (
+        <div key={i} className="space-y-4">
+          <div className="h-3.5 bg-muted rounded w-24 animate-pulse" />
+          <div className="grid grid-cols-2 gap-4">
+            <div className="space-y-2">
+              <div className="h-3.5 bg-muted rounded w-20 animate-pulse" />
+              <div className="h-10 bg-muted rounded animate-pulse" />
+            </div>
+            <div className="space-y-2">
+              <div className="h-3.5 bg-muted rounded w-28 animate-pulse" />
+              <div className="h-10 bg-muted rounded animate-pulse" />
+            </div>
+          </div>
+          <div className="space-y-2">
+            <div className="h-3.5 bg-muted rounded w-16 animate-pulse" />
+            <div className="h-10 bg-muted rounded animate-pulse" />
+          </div>
+        </div>
+      ))}
+    </div>
+  )
+}