feat: add independent load_factor field for scheduling load calculation

- Separate load factor from concurrency: concurrency controls actual
  slot acquisition, load_factor controls load rate calculation
- Add EffectiveLoadFactor() method: LoadFactor > Concurrency > 1
- Add load_factor field to Create/Edit/BulkEdit account forms
- Fix RPM default value: auto-fill 15 when RPM enabled but not set
- Fix stale test compilation errors in server and handler packages

backend/internal/server/api_contract_test.go

@@ -1096,6 +1096,14 @@ func (s *stubAccountRepo) UpdateExtra(ctx context.Context, id int64, updates map
 	return errors.New("not implemented")
 }
 
+func (s *stubAccountRepo) IncrementQuotaUsed(ctx context.Context, id int64, amount float64) error {
+	return errors.New("not implemented")
+}
+
+func (s *stubAccountRepo) ResetQuotaUsed(ctx context.Context, id int64) error {
+	return errors.New("not implemented")
+}
+
 func (s *stubAccountRepo) BulkUpdate(ctx context.Context, ids []int64, updates service.AccountBulkUpdate) (int64, error) {
 	s.bulkUpdateIDs = append([]int64{}, ids...)
 	return int64(len(ids)), nil
@@ -1617,10 +1625,6 @@ func (r *stubUsageLogRepo) GetGroupStatsWithFilters(ctx context.Context, startTi
 	return nil, errors.New("not implemented")
 }
 
-func (r *stubUsageLogRepo) GetGroupStatsWithFilters(ctx context.Context, startTime, endTime time.Time, userID, apiKeyID, accountID, groupID int64, stream *bool, billingType *int8) ([]usagestats.GroupStat, error) {
-	return nil, errors.New("not implemented")
-}
-
 func (r *stubUsageLogRepo) GetAPIKeyUsageTrend(ctx context.Context, startTime, endTime time.Time, granularity string, limit int) ([]usagestats.APIKeyUsageTrendPoint, error) {
 	return nil, errors.New("not implemented")
 }

backend/internal/server/router_test.go

@@ -1,36 +0,0 @@
-//go:build unit
-
-package server
-
-import (
-	"testing"
-
-	"github.com/stretchr/testify/assert"
-)
-
-func TestExtractOrigin(t *testing.T) {
-	tests := []struct {
-		name  string
-		input string
-		want  string
-	}{
-		{"empty string", "", ""},
-		{"whitespace only", "   ", ""},
-		{"valid https", "https://pay.example.com/checkout", "https://pay.example.com"},
-		{"valid http", "http://pay.example.com/checkout", "http://pay.example.com"},
-		{"https with port", "https://pay.example.com:8443/checkout", "https://pay.example.com:8443"},
-		{"protocol-relative //host", "//pay.example.com/path", ""},
-		{"no scheme", "pay.example.com/path", ""},
-		{"ftp scheme rejected", "ftp://pay.example.com/file", ""},
-		{"empty host after parse", "https:///path", ""},
-		{"invalid url", "://bad url", ""},
-		{"only scheme", "https://", ""},
-	}
-
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			got := extractOrigin(tt.input)
-			assert.Equal(t, tt.want, got)
-		})
-	}
-}