Client panic via out-of-range power-level conversion

Incorrect calculation in matrix-sdk-base before 0.14.1 allows remote attackers to trigger a client panic through a minimum power level. RoomMember::normalized_power_level multiplies the signed Matrix integer by 100 and converts the result to bounded Int without first constraining it, so Int::Min produces an out-of-range conversion that panics. The method is not called internally; exposure requires an integrating client to invoke it on attacker-controlled room-member state, and the bounded consequence is interruption of that client process.