[CP-SEED-01] Seed script with demo campaign, 5 team members, 20 voters across 3 territories

## CP-SEED-01: Seed script with demo campaign, 5 team members, 20 voters across 3 territories Section: Demo Data | Milestone: M3 | Owner: AG Lu ### Failing Tests - **seed_file** (file_exists): File `campaignpro/supabase/seed.sql` must exist ### Acceptance Criteria - File `campaignpro/supabase/seed.sql` must exist ### Codebase Conventions - Trilingual comments: // EN: ... // VI: ... // ES: ... - SPEC section refs in comments - Zod at module level with .safeParse() - (supabase as any) with eslint-disable - NextResponse.json() responses - Error format: { error: 'message' }