Created / Updated fields for clients (#3384)

* feat(backend): add created_at/updated_at to clients and maintain on create/update
backfill existing clients and set updated_at on mutations

* feat(frontend): carry created_at/updated_at in client models and round-trip via JSON

* feat(frontend): display Created and Updated columns in client table with proper date formatting

* i18n: add pages.inbounds.createdAt/updatedAt across all locales

* Update inbound.go

Remove duplicate code

web/html/inbounds.html

@@ -760,6 +760,8 @@
         { title: '{{ i18n "pages.inbounds.client" }}', width: 80, scopedSlots: { customRender: 'client' } },
         { title: '{{ i18n "pages.inbounds.traffic" }}', width: 80, align: 'center', scopedSlots: { customRender: 'traffic' } },
         { title: '{{ i18n "pages.inbounds.expireDate" }}', width: 80, align: 'center', scopedSlots: { customRender: 'expiryTime' } },
+        { title: '{{ i18n "pages.inbounds.createdAt" }}', width: 90, align: 'center', scopedSlots: { customRender: 'createdAt' } },
+        { title: '{{ i18n "pages.inbounds.updatedAt" }}', width: 90, align: 'center', scopedSlots: { customRender: 'updatedAt' } },
     ];
 
     const innerMobileColumns = [