feat: self-ban on auto-ban — bot bans itself from blacklisted servers

serverwhitelist/serverwhitelist.py

@@ -527,6 +527,48 @@ class ServerWhitelist(commands.Cog):
             log.warning("Could not DM owner %s (%d): %s", owner, owner.id, exc)
             return False
 
+    # ── self-ban ──────────────────────────────────────────────
+
+    async def _self_ban(self, guild: discord.Guild) -> bool:
+        """Attempt to ban the bot itself from the server.
+
+        This prevents the server from re-inviting the bot until they
+        manually unban it.  Requires the bot to have ``ban_members``
+        permission in the guild — if it doesn't, we silently fall back
+        to a normal leave.
+
+        Returns True if the self-ban succeeded, False otherwise.
+        """
+        me = guild.me
+        if me is None:
+            return False
+
+        # Check if the bot has ban_members permission
+        if not me.guild_permissions.ban_members:
+            log.info(
+                "Cannot self-ban from %s (%d) — missing ban_members permission.",
+                guild.name, guild.id,
+            )
+            return False
+
+        try:
+            await guild.ban(
+                me,
+                reason="ServerWhitelist: Auto-ban — this server is blacklisted.",
+                delete_message_days=0,
+            )
+            log.info("Self-banned from guild %s (%d).", guild.name, guild.id)
+            return True
+        except discord.Forbidden:
+            log.warning(
+                "Self-ban forbidden in %s (%d) despite having permission (role hierarchy?).",
+                guild.name, guild.id,
+            )
+            return False
+        except discord.HTTPException as exc:
+            log.warning("Self-ban failed in %s (%d): %s", guild.name, guild.id, exc)
+            return False
+
     # ── attempt tracking ──────────────────────────────────────
 
     async def _record_attempt(self, guild: discord.Guild) -> tuple[int, bool]:
@@ -612,14 +654,22 @@ class ServerWhitelist(commands.Cog):
                 reason="This server is *permanently blacklisted* and cannot use this bot.",
                 extra="⛔ This server has been *banned*. Continued attempts will be ignored.",
             )
+            # Attempt to self-ban (prevents re-invite until manually unbanned)
+            self_banned = await self._self_ban(guild)
+
+            ban_note = "✅ Bot self-banned from server." if self_banned else "⚠️ Could not self-ban (missing permission) — left normally."
             await self._log_event(
                 title="🚫 Blocked — Blacklisted Server",
                 description=f"Rejected join to **blacklisted** server **{guild.name}**.",
                 colour=0xE74C3C,
-                fields=log_fields + [("Attempts", str(count), True)],
+                fields=log_fields + [
+                    ("Attempts", str(count), True),
+                    ("Self-Ban", ban_note, False),
+                ],
                 thumbnail_url=icon_url,
             )
-            await guild.leave()
+            if not self_banned:
+                await guild.leave()
             return
 
         # ── Locked mode ──────────────────────────────────────
@@ -654,9 +704,9 @@ class ServerWhitelist(commands.Cog):
             if auto_banned:
                 extra = (
                     f"🚨 *This server has been automatically banned after "
-                    f"{count} unauthorized join attempt(s).* The bot will *never* "
-                    f"join this server again. Contact the bot owner if you believe "
-                    f"this is a mistake."
+                    f"{count} unauthorized join attempt(s).* The bot has banned "
+                    f"itself from this server and will *never* join again. "
+                    f"Contact the bot owner if you believe this is a mistake."
                 )
                 reason = f"Not whitelisted — *auto-banned* after {count}/{max_attempts} attempts."
             elif remaining <= 2 and remaining > 0:
@@ -694,17 +744,28 @@ class ServerWhitelist(commands.Cog):
                 log_title = f"⛔ Non-Whitelisted Join (Attempt {count}/{max_attempts})"
                 log_desc = f"Rejected **{guild.name}** — not on the whitelist."
 
+            # If auto-banned this attempt, try to self-ban from the server
+            self_banned = False
+            if auto_banned:
+                self_banned = await self._self_ban(guild)
+
+            extra_fields = [
+                ("Attempts", f"{count}/{max_attempts}", True),
+                ("Remaining", str(remaining) if not auto_banned else "BANNED", True),
+            ]
+            if auto_banned:
+                ban_note = "✅ Bot self-banned from server." if self_banned else "⚠️ Could not self-ban (missing permission) — left normally."
+                extra_fields.append(("Self-Ban", ban_note, False))
+
             await self._log_event(
                 title=log_title,
                 description=log_desc,
                 colour=log_colour,
-                fields=log_fields + [
-                    ("Attempts", f"{count}/{max_attempts}", True),
-                    ("Remaining", str(remaining) if not auto_banned else "BANNED", True),
-                ],
+                fields=log_fields + extra_fields,
                 thumbnail_url=icon_url,
             )
-            await guild.leave()
+            if not self_banned:
+                await guild.leave()
             return
 
         # ── Allowed — whitelisted ────────────────────────────