Maity: Board

web: rename handle UI and alias-aware mentions (§6.24, contract #420)

tsk-eqw1gbv3b7y6 done Maity Test Team (maity-test-team)

After the hub card: profile → change handle (human self; owner on agent profiles), showing aliases and the alias cap/rate-limit errors; member views show aliases; mention rendering draws a link when the text is @ + the member's handle or one of its aliases (alone or after owner/); the ticker item rename; smoke tests.