feat: preview de placement en pipeline de creatividades

Cada pieza muestra mock Meta/Google Ads o RRSS (feed, Stories, LinkedIn) como el Ad Tracker, con copy, media y canal editables.

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

sql/creatives_preview.sql

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+-- Preview fields for creatives pipeline (ads + RRSS placement mocks)
+-- Idempotent.
+
+alter table public.creatives
+  add column if not exists channel text;
+
+alter table public.creatives
+  add column if not exists placement text;
+
+alter table public.creatives
+  add column if not exists format text;
+
+alter table public.creatives
+  add column if not exists headline text;
+
+alter table public.creatives
+  add column if not exists primary_text text;
+
+alter table public.creatives
+  add column if not exists description text;
+
+alter table public.creatives
+  add column if not exists cta text;
+
+alter table public.creatives
+  add column if not exists media_url text;
+
+alter table public.creatives
+  add column if not exists brand_name text;
+
+alter table public.creatives
+  add column if not exists landing_url text;
+
+alter table public.creatives
+  add column if not exists meta jsonb not null default '{}'::jsonb;
+
+-- Soft checks (nullable for legacy rows)
+do $$
+begin
+  if not exists (
+    select 1 from pg_constraint where conname = 'creatives_channel_check'
+  ) then
+    alter table public.creatives
+      add constraint creatives_channel_check
+      check (
+        channel is null
+        or channel in (
+          'meta_ads',
+          'google_ads',
+          'instagram',
+          'facebook',
+          'linkedin',
+          'tiktok',
+          'stories',
+          'other'
+        )
+      );
+  end if;
+end $$;
+
+do $$
+begin
+  if not exists (
+    select 1 from pg_constraint where conname = 'creatives_format_check'
+  ) then
+    alter table public.creatives
+      add constraint creatives_format_check
+      check (
+        format is null
+        or format in (
+          'image',
+          'video',
+          'carousel',
+          'reel',
+          'story',
+          'rsa',
+          'pmax',
+          'other'
+        )
+      );
+  end if;
+end $$;
+
+comment on column public.creatives.channel is
+  'Surface: meta_ads | google_ads | instagram | facebook | linkedin | stories…';
+comment on column public.creatives.placement is
+  'Placement mock: feed | stories | reels | search | display…';
+comment on column public.creatives.media_url is
+  'Public or signed URL for creative media preview';