feat: move user aliases from config to DB with /bcs-alias command

Aliases now stored in UserState table instead of config.yaml. Adds
Aliases column (NVARCHAR 500), loads on startup, persists via flush.
New /bcs-alias slash command (view/set/clear) for managing nicknames.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

config.yaml

@@ -21,13 +21,6 @@ sentiment:
   escalation_threshold: 0.25  # Triage toxicity score that triggers re-analysis with heavy model
   escalation_boost: 0.04  # Per-message drama boost after warning (sustained toxicity ramps toward mute)
 
-# Nicknames/aliases for server members. Used by the LLM to recognize
-# when someone references another member by name in chat.
-user_aliases:
-  684222822272598058: ["Mark", "Limit"]           # thelimitations
-  1113144994790903908: ["Glam", "G"]              # Glamgirlxx
-  1195191381929508964: ["Bree"]                   # QueenBree10
-
 game_channels:
   gta-online: "GTA Online"
   battlefield: "Battlefield"