fix: merge 30 general improvements from release branch

Bug fixes:
- Detached context for GetAccountConcurrencyBatch (prevent all-zero on request cancel)
- Filter soft-deleted users in GetByGroupID
- Stripe CSP policy (allow Stripe.js in script-src and frame-src)
- WebSearch API key validation on save
- RECHARGING status in payment result success check
- Windows test fixes (logger Sync deadlock, config path escaping)

Feature enhancements:
- Webhook multi-instance dispatch (extractOutTradeNo + GetWebhookProvider)
- EasyPay mobile H5 payment (device param + PayURL2)
- SSE error propagation in WebSearch emulation
- AccountStatsCost DTO field for admin usage logs
- Plans sort by sort_order instead of created_at
- UsageMapHook for streaming response usage data
- apicompat Instructions field passthrough
- EffectiveLoadFactor for ops concurrency/metrics
- Usage billing RETURNING balance for notify system
- BulkUpdate mixed channel warning with details
- println to slog migration in auth cache
- Wire ProviderSet cleanup
- CI cache-dependency-path optimization

Frontend:
- Refund eligibility check per provider (canRequestRefund)
- Plan sort_order editing
- Dead code cleanup (simulate_claude_max, client_affinity)
- GroupsView platform switch guard
- channels features_config API type
- UsageView account_stats_cost export

backend/internal/service/concurrency_service.go

@@ -343,8 +343,9 @@ func (s *ConcurrencyService) StartSlotCleanupWorker(accountRepo AccountRepositor
 	}()
 }
 
-// GetAccountConcurrencyBatch gets current concurrency counts for multiple accounts
-// Returns a map of accountID -> current concurrency count
+// GetAccountConcurrencyBatch gets current concurrency counts for multiple accounts.
+// Uses a detached context with timeout to prevent HTTP request cancellation from
+// causing the entire batch to fail (which would show all concurrency as 0).
 func (s *ConcurrencyService) GetAccountConcurrencyBatch(ctx context.Context, accountIDs []int64) (map[int64]int, error) {
 	if len(accountIDs) == 0 {
 		return map[int64]int{}, nil
@@ -356,5 +357,11 @@ func (s *ConcurrencyService) GetAccountConcurrencyBatch(ctx context.Context, acc
 		}
 		return result, nil
 	}
-	return s.cache.GetAccountConcurrencyBatch(ctx, accountIDs)
+
+	// Use a detached context so that a cancelled HTTP request doesn't cause
+	// the Redis pipeline to fail and return all-zero concurrency counts.
+	redisCtx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
+	defer cancel()
+
+	return s.cache.GetAccountConcurrencyBatch(redisCtx, accountIDs)
 }