feat(admin): Add email search and rate limit filtering for accounts and redeem codes

- Add used_by_email column to redeem code export CSV for better user identification
- Implement rate_limited status filter in account listing with RateLimitResetAt check
- Extend redeem code search to include user email in addition to code matching
- Add API key search capability to user listing filters
- Display user email in redeem code table used_by column for improved visibility
- Update search placeholders in UI to reflect expanded search capabilities (email, username, notes, API key)
- Improve Chinese and English localization strings for search hints

backend/internal/repository/account_repo.go

@@ -448,7 +448,12 @@ func (r *accountRepository) ListWithFilters(ctx context.Context, params paginati
 		q = q.Where(dbaccount.TypeEQ(accountType))
 	}
 	if status != "" {
-		q = q.Where(dbaccount.StatusEQ(status))
+		switch status {
+		case "rate_limited":
+			q = q.Where(dbaccount.RateLimitResetAtGT(time.Now()))
+		default:
+			q = q.Where(dbaccount.StatusEQ(status))
+		}
 	}
 	if search != "" {
 		q = q.Where(dbaccount.NameContainsFold(search))

backend/internal/repository/redeem_code_repo.go

@@ -6,6 +6,7 @@ import (
 
 	dbent "github.com/Wei-Shaw/sub2api/ent"
 	"github.com/Wei-Shaw/sub2api/ent/redeemcode"
+	"github.com/Wei-Shaw/sub2api/ent/user"
 	"github.com/Wei-Shaw/sub2api/internal/pkg/pagination"
 	"github.com/Wei-Shaw/sub2api/internal/service"
 )
@@ -106,7 +107,12 @@ func (r *redeemCodeRepository) ListWithFilters(ctx context.Context, params pagin
 		q = q.Where(redeemcode.StatusEQ(status))
 	}
 	if search != "" {
-		q = q.Where(redeemcode.CodeContainsFold(search))
+		q = q.Where(
+			redeemcode.Or(
+				redeemcode.CodeContainsFold(search),
+				redeemcode.HasUserWith(user.EmailContainsFold(search)),
+			),
+		)
 	}
 
 	total, err := q.Count(ctx)

backend/internal/repository/user_repo.go

@@ -10,6 +10,7 @@ import (
 	"time"
 
 	dbent "github.com/Wei-Shaw/sub2api/ent"
+	"github.com/Wei-Shaw/sub2api/ent/apikey"
 	dbuser "github.com/Wei-Shaw/sub2api/ent/user"
 	"github.com/Wei-Shaw/sub2api/ent/userallowedgroup"
 	"github.com/Wei-Shaw/sub2api/ent/usersubscription"
@@ -191,6 +192,7 @@ func (r *userRepository) ListWithFilters(ctx context.Context, params pagination.
 				dbuser.EmailContainsFold(filters.Search),
 				dbuser.UsernameContainsFold(filters.Search),
 				dbuser.NotesContainsFold(filters.Search),
+				dbuser.HasAPIKeysWith(apikey.KeyContainsFold(filters.Search)),
 			),
 		)
 	}