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/useSettings.ts

@@ -0,0 +1,41 @@
+'use client'
+
+import { useState, useEffect, useCallback } from 'react'
+import { useRouter } from 'next/navigation'
+import { createClient } from '@/lib/supabase/client'
+import { useCompany } from '@/contexts/CompanyContext'
+import type { CompanySettings } from '@/types'
+
+export function useSettings() {
+  const router = useRouter()
+  const { company } = useCompany()
+  const [settings, setSettings] = useState<CompanySettings | null>(null)
+  const [isLoading, setIsLoading] = useState(true)
+
+  const fetchSettings = useCallback(async () => {
+    const supabase = createClient()
+    const { data: { user } } = await supabase.auth.getUser()
+    if (!user) { router.push('/login'); return }
+
+    if (company?.id) {
+      const { data } = await supabase
+        .from('company_settings')
+        .select('*')
+        .eq('company_id', company.id)
+        .single()
+      setSettings(data)
+    }
+
+    setIsLoading(false)
+  }, [company?.id, router])
+
+  useEffect(() => {
+    fetchSettings()
+  }, [fetchSettings])
+
+  const updateSettings = useCallback((updates: Partial<CompanySettings>) => {
+    setSettings(prev => prev ? { ...prev, ...updates } as CompanySettings : null)
+  }, [])
+
+  return { settings, isLoading, updateSettings, refetch: fetchSettings }
+}