fix(node-traffic): prevent stale node snapshot from re-enabling disabled client (#4917)

When a remote node syncs traffic back to the panel, the UPDATE in
setRemoteTrafficLocked wrote cs.Enable directly into client_traffics.enable.
If a snapshot carrying enable=true arrived after the central panel had already
set enable=false (due to the client reaching their traffic limit), it silently
re-enabled the client — letting them consume 2-3x their allotted quota before
the next disable cycle caught up.

Fix: replace the unconditional SET enable = ? with a CASE expression that only
allows a disable (0->0), never a re-enable (0->1). The central panel remains
the sole authority for turning a client back on.

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
Co-authored-by: Sanaei <ho3ein.sanaei@gmail.com>

web/service/inbound.go

@@ -1615,12 +1615,19 @@ func (s *InboundService) setRemoteTrafficLocked(nodeID int, snap *runtime.Traffi
 				structuralChange = true
 			}
 
+			// Only allow the node to disable a client (cs.Enable=false), never
+			// to re-enable one the panel has already disabled. A stale snapshot
+			// from the node arriving after a central disable would otherwise
+			// overwrite enable=false back to true, letting the client accumulate
+			// far more traffic than their limit before being disabled again.
+			enableExpr := "CASE WHEN ? = 0 THEN 0 ELSE enable END"
 			if err := tx.Exec(
 				fmt.Sprintf(
 					`UPDATE client_traffics
-					 SET up = up + ?, down = down + ?, enable = ?, total = ?, expiry_time = ?, reset = ?,
+					 SET up = up + ?, down = down + ?, enable = %s, total = ?, expiry_time = ?, reset = ?,
 					     last_online = %s
 					 WHERE email = ?`,
+					enableExpr,
 					database.GreatestExpr("last_online", "?"),
 				),
 				deltaUp, deltaDown, cs.Enable, cs.Total, cs.ExpiryTime, cs.Reset,