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>

app/api/reports/continuity-check/route.ts

@@ -0,0 +1,36 @@
+import { createClient } from '@/lib/supabase/server'
+import { NextResponse } from 'next/server'
+import { validateBalanceContinuity } from '@/lib/reports/continuity-check'
+import { requireCompanyId } from '@/lib/company/context'
+
+/**
+ * GET: Validate IB/UB continuity for a fiscal period.
+ * Query param: period_id (required)
+ */
+export async function GET(request: Request) {
+  const supabase = await createClient()
+  const { data: { user } } = await supabase.auth.getUser()
+
+  if (!user) {
+    return NextResponse.json({ error: 'Unauthorized' }, { status: 401 })
+  }
+
+  const companyId = await requireCompanyId(supabase, user.id)
+
+  const { searchParams } = new URL(request.url)
+  const periodId = searchParams.get('period_id')
+
+  if (!periodId) {
+    return NextResponse.json({ error: 'period_id is required' }, { status: 400 })
+  }
+
+  try {
+    const result = await validateBalanceContinuity(supabase, companyId, periodId)
+    return NextResponse.json({ data: result })
+  } catch (err) {
+    return NextResponse.json(
+      { error: err instanceof Error ? err.message : 'Failed to validate continuity' },
+      { status: 400 }
+    )
+  }
+}