feat: 完成模拟交易闭环、App 与 A 股行情接入

统一单入口 Go 工程与前端依赖目录，增加后台供应商配置、候选审核、计划预算、成交冲正、持仓复盘和站内通知。接入策略版本、Python 回测、可配置 A 股公开行情及 zap 文件轮转日志，补充迁移、契约与验证。

internal/apperror/errors.go

@@ -1,13 +1,22 @@
 // Package apperror defines safe application errors shared across module boundaries.
 package apperror
 
-import "errors"
+import (
+	"errors"
+	"fmt"
+)
 
 var (
-	ErrInvalidInput    = errors.New("invalid input")
-	ErrUnauthenticated = errors.New("authentication required")
-	ErrForbidden       = errors.New("permission denied")
-	ErrConflict        = errors.New("already exists")
-	ErrNotFound        = errors.New("not found")
-	ErrUnavailable     = errors.New("service unavailable")
+	ErrInvalidInput         = errors.New("invalid input")
+	ErrUnauthenticated      = errors.New("authentication required")
+	ErrForbidden            = errors.New("permission denied")
+	ErrConflict             = errors.New("already exists")
+	ErrInsufficientCash     = fmt.Errorf("insufficient available cash: %w", ErrConflict)
+	ErrInsufficientQuantity = fmt.Errorf("insufficient sellable quantity: %w", ErrConflict)
+	ErrCandidateUnavailable = fmt.Errorf("candidate unavailable: %w", ErrConflict)
+	ErrPreviewExpired       = fmt.Errorf("preview expired: %w", ErrConflict)
+	ErrChronology           = fmt.Errorf("fill chronology conflict: %w", ErrConflict)
+	ErrDependentFill        = fmt.Errorf("later fill depends on this record: %w", ErrConflict)
+	ErrNotFound             = errors.New("not found")
+	ErrUnavailable          = errors.New("service unavailable")
 )