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>

lib/bookkeeping/engine.ts

@@ -209,7 +209,9 @@ export async function createDraftEntry(
 
 /**
  * Commit a draft entry: assigns voucher number and transitions to 'posted'
- * Triggers balance validation and sets committed_at via DB triggers
+ * Uses the atomic commit_journal_entry RPC so the voucher number increment
+ * and status update happen in one transaction. If the balance trigger rejects
+ * the entry, the sequence increment rolls back — no burned numbers.
  */
 export async function commitEntry(
   supabase: SupabaseClient,
@@ -218,39 +220,15 @@ export async function commitEntry(
   entryId: string
 ): Promise<JournalEntry> {
 
-  // Fetch the draft entry
-  const { data: entry, error: fetchError } = await supabase
-    .from('journal_entries')
-    .select('*')
-    .eq('id', entryId)
-    .eq('company_id', companyId)
-    .eq('status', 'draft')
-    .single()
+  // Atomic: increment voucher sequence + update status in one transaction.
+  // Rolls back the sequence if the balance trigger or any constraint fails.
+  const { data: rpcResult, error: commitError } = await supabase.rpc('commit_journal_entry', {
+    p_company_id: companyId,
+    p_entry_id: entryId,
+  })
 
-  if (fetchError || !entry) {
-    throw new Error('Draft journal entry not found')
-  }
-
-  // Assign voucher number
-  const voucherNumber = await getNextVoucherNumber(
-    supabase,
-    companyId,
-    entry.fiscal_period_id,
-    entry.voucher_series || 'A'
-  )
-
-  // Update to posted with voucher number
-  // DB triggers will: validate balance, set committed_at, write audit log
-  const { error: postError } = await supabase
-    .from('journal_entries')
-    .update({
-      voucher_number: voucherNumber,
-      status: 'posted',
-    })
-    .eq('id', entryId)
-
-  if (postError) {
-    throw new Error(`Failed to commit journal entry: ${postError.message}`)
+  if (commitError) {
+    throw new Error(`Failed to commit journal entry: ${commitError.message}`)
   }
 
   // Fetch complete posted entry with lines