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

frontend/src/pages/xray/routing/RoutingTab.tsx

@@ -1,10 +1,11 @@
 import { useCallback, useMemo, useRef, useState } from 'react';
 import { useTranslation } from 'react-i18next';
 import { Button, Modal, Space, Table, Tabs } from 'antd';
-import { ControlOutlined, PlusOutlined, UnorderedListOutlined } from '@ant-design/icons';
+import { AimOutlined, ControlOutlined, PlusOutlined, UnorderedListOutlined } from '@ant-design/icons';
 
 import { catTabLabel } from '@/pages/settings/catTabLabel';
 import RoutingBasic from './RoutingBasic';
+import RouteTester from './RouteTester';
 import RuleFormModal from './RuleFormModal';
 import type { RoutingRule } from './RuleFormModal';
 import RuleCardList from './RuleCardList';
@@ -312,6 +313,11 @@ export default function RoutingTab({
               </Space>
             ),
           },
+          {
+            key: 'tester',
+            label: catTabLabel(<AimOutlined />, t('pages.xray.routeTester'), isMobile),
+            children: <RouteTester inboundTags={inboundTagOptions} isMobile={isMobile} />,
+          },
         ]}
       />
       <RuleFormModal