fix: enhance WebSocket stability, resolve XHTTP configurations and fix UI loading shifts (#3997)

* feat: implement real-time traffic monitoring and UI updates using a high-performance WebSocket hub and background job system

* feat: add bulk client management support and improve inbound data handling

* Fix bug

* **Fixes & Changes:**
1. **Fixed XPadding Placement Dropdown**:
   - Added the missing `cookie` and `query` options to `xPaddingPlacement` (`stream_xhttp.html`).
   - *Why:* Previously, users wanting `cookie` obfuscation were forced to use the `header` placement string. This caused Xray-core to blindly intercept the entire monolithic HTTP Cookie header, failing internal padding-length validations and causing the inbound to silently drop the connection.
2. **Fixed Uplink Data Placement Validation**:
   - Replaced the unsupported `query` option with `cookie` in `uplinkDataPlacement`.
   - *Why:* Xray-core's `transport_internet.go` explicitly forbids `query` as an uplink placement option. Selecting it from the UI previously sent a payload that would cause Xray-core to instantly throw an `unsupported uplink data placement: query` panic. Adding `cookie` perfectly aligns the UI with Xray-core restrictions.
### Related Issues
- Resolves #3992

* This commit fixes structural payload issues preventing XHTTP from functioning correctly and eliminates WebSocket log spam.
- **[Fix X-Padding UI]** Added missing `cookie` and `query` options to X-Padding Placement. Fixes the issue where using Cookie fallback triggers whole HTTP Cookie header interception and silent drop in Xray-core. (Resolves [#3992](https://github.com/MHSanaei/3x-ui/issues/3992))
- **[Fix Uplink Data Options]** Replaced the invalid `query` option with `cookie` in Uplink Data Placement dropdown to prevent Xray-core backend panic `unsupported uplink data placement: query`.
- **[Fix WebSockets Spam]** Boosted `maxMessageSize` boundary to 100MB and gracefully handled fallback fetch signals via `broadcastInvalidate` to avoid buffer dropping spam. (Resolves [#3984](https://github.com/MHSanaei/3x-ui/issues/3984))

* Fix

* gofmt

* fix(websocket): resolve channel race condition and graceful shutdown deadlock

* Fix: inbounds switch

* Change max quantity from 10000 to 500

* fix

web/websocket/notifier.go

@@ -24,6 +24,16 @@ func GetHub() *Hub {
 	return wsHub
 }
 
+// HasClients returns true if there are any WebSocket clients connected.
+// Use this to skip expensive work (DB queries, serialization) when no browser is open.
+func HasClients() bool {
+	hub := GetHub()
+	if hub == nil {
+		return false
+	}
+	return hub.GetClientCount() > 0
+}
+
 // BroadcastStatus broadcasts server status update to all connected clients
 func BroadcastStatus(status any) {
 	hub := GetHub()
@@ -80,3 +90,14 @@ func BroadcastXrayState(state string, errorMsg string) {
 		hub.Broadcast(MessageTypeXrayState, stateUpdate)
 	}
 }
+
+// BroadcastInvalidate sends a lightweight invalidate signal for the given data type,
+// telling connected frontends to re-fetch data via REST API.
+// Use this instead of BroadcastInbounds/BroadcastOutbounds when you know the payload
+// will be too large, to avoid wasting resources on serialization.
+func BroadcastInvalidate(dataType MessageType) {
+	hub := GetHub()
+	if hub != nil {
+		hub.broadcastInvalidate(dataType)
+	}
+}