Combat overhaul & enhancement rework

Damage reduction reworked. DR now applies cleanly to your full stats instead of stacking in ways that made armor feel inconsistent. Weapons actually feel different from each other now.

Enhancement system rebuilt. Items can be enhanced to amplify their stats, and the curve is tuned so that investing in a rare item you like can outperform an unenhanced epic. Meaningful choices over rarity chasing.

Fixed off-hand penalty applying twice, weapon speed now properly affects combat timing, and enemy scaling matches what players can actually build so fights stay competitive.