feat: KPIs con totales absolutos, backfill ads y ventas en cruce canal

Comparativas WoW/MoM/YoY muestran prev/Δ además del %; sync ads admite
histórico desde 2025; tabla ads↔CRM añade cierres, ventas y ROAS.

Co-authored-by: Cursor <cursoragent@cursor.com>

sql/leads_status_timing.sql

@@ -0,0 +1,22 @@
+-- CRM date correctness: preserve lead birth vs status change timing.
+-- Run in Supabase SQL editor (service role / dashboard).
+
+alter table public.leads
+  add column if not exists updated_at timestamptz;
+
+alter table public.leads
+  add column if not exists status_changed_at timestamptz;
+
+comment on column public.leads.created_at is
+  'When the contact entered Clientify / first seen (alta).';
+comment on column public.leads.updated_at is
+  'Last webhook/sync touch.';
+comment on column public.leads.status_changed_at is
+  'When status last changed (e.g. → cliente). Use this for “ventas en el periodo”.';
+
+-- Backfill: unknown status timing → treat as created_at (best effort).
+update public.leads
+set
+  updated_at = coalesce(updated_at, created_at, now()),
+  status_changed_at = coalesce(status_changed_at, created_at, now())
+where updated_at is null or status_changed_at is null;