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/20260709000008_seed.sql

@@ -0,0 +1,34 @@
+-- supabase/migrations/20260709000008_seed.sql
+-- Test site: Setia Corp Warehouse 1
+INSERT INTO sites (id, name, address, region, active)
+VALUES (
+  '00000000-0000-0000-0000-000000000001'::UUID,
+  'SCW1',
+  'No. 1, Jalan Industri 1, Shah Alam, Selangor',
+  'Central',
+  true
+)
+ON CONFLICT (id) DO NOTHING;
+
+-- Zones for SCW1
+INSERT INTO zones (id, site_id, name, qr_code_token)
+VALUES
+  (
+    '00000000-0000-0000-0000-000000000010'::UUID,
+    '00000000-0000-0000-0000-000000000001'::UUID,
+    'Dock A',
+    'scw1-dock-a-qr-2026'
+  ),
+  (
+    '00000000-0000-0000-0000-000000000011'::UUID,
+    '00000000-0000-0000-0000-000000000001'::UUID,
+    'Cold Storage',
+    'scw1-cold-storage-qr-2026'
+  ),
+  (
+    '00000000-0000-0000-0000-000000000012'::UUID,
+    '00000000-0000-0000-0000-000000000001'::UUID,
+    'Loading Bay',
+    'scw1-loading-bay-qr-2026'
+  )
+ON CONFLICT (id) DO NOTHING;