Rebrand welcome messages and re-enable drop-roll debug logging

Welcome message default/example changed from "Welcome to ROSE" to
"Welcome to ROSS", and the hardcoded post-login system message
replaced with a ROSS-specific credit line.

Also re-enable the codedebug SendPM lines in GetNewDrop that report
the raw randv/money/zulyrate/item/itemrate values behind each
zuly-vs-item roll (previously commented out) -- needed to diagnose
in-game why item drops are still rare/absent after the drop-rate and
item-index fixes, without guessing at STB drop-table values blind.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

.env.example

@@ -22,7 +22,7 @@ WORLD_PORT=29200
 LOGIN_SERVER_NAME=ROSE Login
 CHAR_SERVER_NAME=Server 1
 WORLD_CHANNEL_NAME=Channel 1
-WORLD_WELCOME_MSG=Welcome to ROSE
+WORLD_WELCOME_MSG=Welcome to ROSS
 
 # --- Gameplay knobs ---------------------------------------------------------
 WORLD_MAX_CONNECTIONS=500