feat: add database schema migrations and seed data

8 SQL migration files covering all 10 tables, RLS policies with
SECURITY DEFINER helpers, and seed data for SCW1 site + 3 zones.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AWxyMibCuGGtSQSqfajDQ7

supabase/migrations/20260709000006_notifications_audit.sql

@@ -0,0 +1,26 @@
+-- supabase/migrations/20260709000006_notifications_audit.sql
+CREATE TYPE notification_channel AS ENUM ('email', 'whatsapp', 'in_app');
+
+CREATE TABLE notifications_log (
+  id          UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+  incident_id UUID REFERENCES incidents(id),
+  capa_id     UUID REFERENCES capa_actions(id),
+  channel     notification_channel NOT NULL,
+  recipient   TEXT NOT NULL,
+  sent_at     TIMESTAMPTZ NOT NULL DEFAULT now(),
+  status      TEXT NOT NULL DEFAULT 'sent'
+);
+
+CREATE TABLE audit_log (
+  id         UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+  table_name TEXT NOT NULL,
+  record_id  UUID NOT NULL,
+  action     TEXT NOT NULL,
+  changed_by UUID REFERENCES users(id),
+  changed_at TIMESTAMPTZ NOT NULL DEFAULT now(),
+  old_value  JSONB,
+  new_value  JSONB
+);
+
+CREATE INDEX audit_log_table_record_idx ON audit_log(table_name, record_id);
+CREATE INDEX audit_log_changed_by_idx   ON audit_log(changed_by);