Function addPlayerToTeam

addPlayerToTeam(playerId: string, teamId: string): Promise<void>
Add playerId to team.playerIds AND teamId to player.teamIds in a single atomic transaction.

Safe to call when the relationship already exists — idempotent.
Parameters
- playerId: string
- teamId: string
Returns Promise<void>
- Defined in src/db/players-teams.ts:18