Adds GET :id/overview/stats + TeamsService#getOverviewStats, aggregating
team-wallet and player payment transactions into a 12-month balanceHistory
(cumulative, carry-forward), monthlyFlow (income/expense), and topOutstanding
(top 10 active debtors) for the upcoming overview KPI charts. fine/levy/fee
and player-level credit are excluded, matching the "Ist-Kasse" cash-flow rule.
Replaces the unmodified NestJS-boilerplate placeholder specs for
TeamsService/TeamsController (which already failed at baseline) with real
tests using the team-access.service.spec.ts direct-construction convention.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
ecb6fd4394