feat: apply inbound/outbound/routing changes live via Xray gRPC API

Add a hot-apply layer that computes a diff between the old and new
generated config and applies only the changed parts through the Xray
gRPC HandlerService and RoutingService, avoiding a full process restart
whenever possible. A restart is still performed when sections that have
no reload API (log, dns, policy, observatory, ...) actually change.

Key additions:
- internal/xray/hot_diff.go: ComputeHotDiff with canonical-JSON
  comparison (sorted keys, null=absent, full number precision) so UI
  reformatting never triggers a spurious restart
- internal/xray/api.go: AddOutbound/DelOutbound, ApplyRoutingConfig,
  GetBalancerInfo, SetBalancerTarget, TestRoute gRPC wrappers
- internal/web/service/xray.go: tryHotApply, ensureAPIServices,
  GetBalancersStatus, OverrideBalancer, TestRoute service methods
- internal/web/controller/xray_setting.go: balancerStatus,
  balancerOverride, routeTest API endpoints
- frontend: BalancersTab live-status/override columns, RouteTester
  component, Restart button removed (Save now hot-applies)
- balancer-helpers.ts: syncObservatories never creates observatory
  sections for random/roundRobin balancers (no reload API → restart)
- i18n: balancerLive/Override/routeTester keys added to all 13 locales

internal/xray/process.go

@@ -249,6 +249,13 @@ func (p *Process) GetConfig() *Config {
 	return p.config
 }
 
+// SetConfig replaces the stored configuration snapshot after the running
+// process has been reconciled with it through the gRPC API (hot apply), so
+// later change detection compares against what is actually running.
+func (p *Process) SetConfig(config *Config) {
+	p.config = config
+}
+
 // GetOnlineClients returns the union of locally-online clients and
 // node-online clients from every registered remote panel. Dedupes by
 // email so a client connected to both a local and a node-managed inbound