feat: global banlist for role creation

GLOBAL_ADMINS env controls who can /gban, /gunban, /gbanlist.
Banned users blocked from /roleadd across all chats.

drizzle/0003_wakeful_doctor_spectrum.sql

@@ -0,0 +1,8 @@
+CREATE TABLE "banned_users" (
+	"id" uuid PRIMARY KEY DEFAULT gen_random_uuid() NOT NULL,
+	"user_id" bigint NOT NULL,
+	"reason" text,
+	"banned_by" bigint NOT NULL,
+	"created_at" timestamp DEFAULT now() NOT NULL,
+	CONSTRAINT "banned_users_user_id_unique" UNIQUE("user_id")
+);