Add a DatabaseSeeder orchestrator (plain 'buddy seed' is a no-op)

[glennmichael123]

Problem

database/seeders/ has per-model seeders but no orchestrator, so buddy seed (no --class) does nothing. Seeding the full world requires running each class, and game data (territories from the engine) isn't seeded at all by the scaffolded seeders — that lives in the ad-hoc scripts/seed-game-world.ts.

Acceptance

• DatabaseSeeder that runs the model seeders in FK order + seeds a real game world (users/activities/engine-produced territories).
• buddy seed populates a coherent demo.