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/TaxSettingsForm.tsx

@@ -0,0 +1,34 @@
+'use client'
+
+import { Input } from '@/components/ui/input'
+import { Label } from '@/components/ui/label'
+import type { CompanySettings } from '@/types'
+
+interface TaxSettingsFormProps {
+  settings: CompanySettings
+}
+
+export function TaxSettingsForm({ settings }: TaxSettingsFormProps) {
+  return (
+    <section className="space-y-4">
+      <h2 className="text-sm font-medium uppercase tracking-wider text-muted-foreground">
+        Preliminärskatt
+      </h2>
+
+      <div className="max-w-xs space-y-2">
+        <Label htmlFor="preliminary_tax_monthly">
+          Månatlig preliminärskatt (F-skatt)
+        </Label>
+        <Input
+          id="preliminary_tax_monthly"
+          name="preliminary_tax_monthly"
+          type="number"
+          defaultValue={settings.preliminary_tax_monthly || ''}
+        />
+        <p className="text-xs text-muted-foreground">
+          Belopp i SEK som betalas varje månad.
+        </p>
+      </div>
+    </section>
+  )
+}