feat(inbounds): bulk-attach & assign-group client actions + form defaults

- Bulk-attach an inbound's clients onto other inbounds (same identity, shared traffic): new ClientService.BulkAttach + POST /clients/bulkAttach, an inbound row action, and AttachClientsModal.
- Assign all of an inbound's clients to a group from the inbound page, reusing /clients/bulkAssignGroup and the existing BulkAssignGroupModal.
- Default a random user/pass account for new Mixed and HTTP inbounds instead of an empty accounts list.
- Capitalize the inbound Security toggle labels (None/TLS/Reality).

frontend/src/lib/xray/inbound-defaults.ts

@@ -185,13 +185,16 @@ export function createDefaultHysteriaInboundSettings(
 }
 
 export function createDefaultHttpInboundSettings(): HttpInboundSettings {
-  return { accounts: [], allowTransparent: false };
+  return {
+    accounts: [{ user: RandomUtil.randomLowerAndNum(8), pass: RandomUtil.randomLowerAndNum(12) }],
+    allowTransparent: false,
+  };
 }
 
 export function createDefaultMixedInboundSettings(): MixedInboundSettings {
   return {
     auth: 'password',
-    accounts: [],
+    accounts: [{ user: RandomUtil.randomLowerAndNum(8), pass: RandomUtil.randomLowerAndNum(12) }],
     udp: false,
     ip: '127.0.0.1',
   };