feat: improve login UX and add admin login lock reset

- Translate all login error messages to Chinese (network errors, HTTP
  status codes, URL validation errors)
- Add password visibility toggle (eye icon) to login form
- Add live countdown timer when login is locked, disable login button
  during cooldown, auto-clear error when countdown ends
- Add X button red hover feedback in server settings dialog
- Add LoginGuard.Unlock() method to clear Redis lock/failure keys
- Expose POST /admin-users/:id/reset-login-lock endpoint in ops API
- Add "重置登录保护" button in ops-web user management table

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

server/internal/ops/transport/admin_user_handler.go

@@ -284,3 +284,18 @@ func resetAdminUserPasswordHandler(svc *app.AdminUserService) gin.HandlerFunc {
 		response.Success(c, gin.H{"id": id})
 	}
 }
+
+func resetAdminUserLoginLockHandler(svc *app.AdminUserService) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		id, err := parseIDParam(c)
+		if err != nil {
+			response.Error(c, err)
+			return
+		}
+		if err := svc.ResetLoginLock(c.Request.Context(), actorFromGin(c), id); err != nil {
+			response.Error(c, err)
+			return
+		}
+		response.Success(c, gin.H{"id": id})
+	}
+}