[Feature] Founder's Package — one-time high-value purchase

## Overview
A one-time purchasable package at a premium price point (~£1,000). Permanent status, exclusive cosmetics, never available again after the window closes. Whale capture mechanic.

## Scope
- One-time purchase (not subscription) via Stripe
- Permanent status indicator in-game
- Exclusive cosmetics not available elsewhere
- Hard cap on number of packages available
- Time or unit limited — countdown/counter in shop

## Decisions needed
- [ ] Price point confirmed
- [ ] Exact perks defined
- [ ] Unit cap confirmed (suggested: 100–250)
- [ ] Time-limited or unit-limited

## Acceptance criteria
- [ ] Purchasable as single Stripe transaction
- [ ] Status persists permanently
- [ ] Exclusive cosmetics applied and never available to non-Founder players
- [ ] Cap enforced in shop — sold out state displayed when reached

## Dependencies
- **Depends on:** OAuth, Stripe, Shop UI redesign