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/import/SIEPreviewStep.tsx

@@ -81,18 +81,14 @@ export default function SIEPreviewStep({
             <div>
               <p className="text-sm text-muted-foreground">Start</p>
               <p className="font-medium">
-                {preview.fiscalYearStart
-                  ? new Date(preview.fiscalYearStart).toLocaleDateString('sv-SE')
-                  : 'Okänt'}
+                {preview.fiscalYearStart ?? 'Okänt'}
               </p>
             </div>
             <ArrowRight className="h-4 w-4 text-muted-foreground" />
             <div>
               <p className="text-sm text-muted-foreground">Slut</p>
               <p className="font-medium">
-                {preview.fiscalYearEnd
-                  ? new Date(preview.fiscalYearEnd).toLocaleDateString('sv-SE')
-                  : 'Okänt'}
+                {preview.fiscalYearEnd ?? 'Okänt'}
               </p>
             </div>
           </div>