Economy rebalance: endgame farming audit

Endgame farming was way too fast. A well-geared player could clear enhancement costs and territory prices in minutes, not hours. Epic items were dropping so frequently they stopped feeling special.

Pulled back XP, scrap, and material rewards across the board. Kill streak bonuses at high thresholds were toned down. Enhancement material drop rates were reduced, especially from elites and minibosses. Epic drops are rarer and feel like actual finds again.

The endgame economy now paces out properly. Enhancement materials are the real bottleneck for gear progression, which is where it should be. Prices and costs weren't touched — the income was the problem, not the sinks.