feat: add GORM integration with repository pattern

- Add GORM models in models/ directory with proper column tags
- Create repository interfaces and implementations in core/repository/
- Add database package with MySQL and SQLite support
- Add UUID ID utility for GORM models
- Implement complete repository layer replacing SQL-based data access
- Add database migrations and index creation
- Support both MySQL and SQLite drivers with auto-migration

🤖 Generated with [Claude Code](https://claude.ai/code)

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

models/account.go

@@ -0,0 +1,18 @@
+package models
+
+// Account represents a financial account
+type Account struct {
+	ID           []byte `gorm:"type:BINARY(16);primaryKey"`
+	OrgID        []byte `gorm:"column:orgId;type:BINARY(16);not null"`
+	Inserted     uint64 `gorm:"column:inserted;not null"`
+	Updated      uint64 `gorm:"column:updated;not null"`
+	Name         string `gorm:"column:name;size:100;not null"`
+	Parent       []byte `gorm:"column:parent;type:BINARY(16);not null"`
+	Currency     string `gorm:"column:currency;size:10;not null"`
+	Precision    int    `gorm:"column:precision;not null"`
+	DebitBalance bool   `gorm:"column:debitBalance;not null"`
+
+	Org      Org       `gorm:"foreignKey:OrgID"`
+	Splits   []Split   `gorm:"foreignKey:AccountID"`
+	Balances []Balance `gorm:"foreignKey:AccountID"`
+}

models/api_key.go

@@ -0,0 +1,13 @@
+package models
+
+// APIKey represents API keys for users
+type APIKey struct {
+	ID       []byte `gorm:"type:BINARY(16);primaryKey"`
+	Inserted uint64 `gorm:"column:inserted;not null"`
+	Updated  uint64 `gorm:"column:updated;not null"`
+	UserID   []byte `gorm:"column:userId;type:BINARY(16);not null"`
+	Label    string `gorm:"column:label;size:300;not null"`
+	Deleted  uint64 `gorm:"column:deleted"`
+
+	User User `gorm:"foreignKey:UserID"`
+}

models/balance.go

@@ -0,0 +1,11 @@
+package models
+
+// Balance represents an account balance at a point in time
+type Balance struct {
+	ID        uint   `gorm:"primaryKey;autoIncrement"`
+	Date      uint64 `gorm:"column:date;not null"`
+	AccountID []byte `gorm:"column:accountId;type:BINARY(16);not null"`
+	Amount    int64  `gorm:"column:amount;not null"`
+
+	Account Account `gorm:"foreignKey:AccountID"`
+}

models/base.go

@@ -0,0 +1,45 @@
+package models
+
+import (
+	"github.com/google/uuid"
+	"github.com/openaccounting/oa-server/core/util/id"
+	"gorm.io/gorm"
+)
+
+type Base struct {
+	ID []byte `gorm:"type:BINARY(16);primaryKey"`
+}
+
+// GetUUID converts binary ID to UUID
+func (b *Base) GetUUID() (uuid.UUID, error) {
+	return id.ToUUID(b.ID)
+}
+
+// GetIDString returns string representation of the ID
+func (b *Base) GetIDString() string {
+	return id.String(b.ID)
+}
+
+// SetIDFromString parses string UUID into binary ID
+func (b *Base) SetIDFromString(s string) error {
+	binID, err := id.FromString(s)
+	if err != nil {
+		return err
+	}
+	b.ID = binID
+	return nil
+}
+
+// ValidateID checks if the ID is a valid UUID
+func (b *Base) ValidateID() error {
+	_, err := uuid.FromBytes(b.ID)
+	return err
+}
+
+// BeforeCreate GORM hook to set ID if empty
+func (b *Base) BeforeCreate(tx *gorm.DB) error {
+	if len(b.ID) == 0 {
+		b.ID = id.New()
+	}
+	return nil
+}

models/budget_item.go

@@ -0,0 +1,13 @@
+package models
+
+// BudgetItem represents budget items
+type BudgetItem struct {
+	ID        uint   `gorm:"primaryKey;autoIncrement"`
+	OrgID     []byte `gorm:"column:orgId;type:BINARY(16);not null"`
+	AccountID []byte `gorm:"column:accountId;type:BINARY(16);not null"`
+	Inserted  uint64 `gorm:"column:inserted;not null"`
+	Amount    int64  `gorm:"column:amount;not null"`
+
+	Org     Org     `gorm:"foreignKey:OrgID"`
+	Account Account `gorm:"foreignKey:AccountID"`
+}

models/invite.go

@@ -0,0 +1,13 @@
+package models
+
+// Invite represents organization invitations
+type Invite struct {
+	ID       string `gorm:"size:32;primaryKey"`
+	OrgID    []byte `gorm:"column:orgId;type:BINARY(16);not null"`
+	Inserted uint64 `gorm:"column:inserted;not null"`
+	Updated  uint64 `gorm:"column:updated;not null"`
+	Email    string `gorm:"column:email;size:100;not null"`
+	Accepted bool   `gorm:"column:accepted;not null"`
+
+	Org Org `gorm:"foreignKey:OrgID"`
+}

models/org.go

@@ -0,0 +1,15 @@
+package models
+
+// Org represents an organization
+type Org struct {
+	ID        []byte `gorm:"type:BINARY(16);primaryKey"`
+	Inserted  uint64 `gorm:"column:inserted;not null"`
+	Updated   uint64 `gorm:"column:updated;not null"`
+	Name      string `gorm:"column:name;size:100;not null"`
+	Currency  string `gorm:"column:currency;size:10;not null"`
+	Precision int    `gorm:"column:precision;not null"`
+	Timezone  string `gorm:"column:timezone;size:100;not null"`
+
+	Accounts []Account `gorm:"foreignKey:OrgID"`
+	UserOrgs []UserOrg `gorm:"foreignKey:OrgID"`
+}

models/permission.go

@@ -0,0 +1,18 @@
+package models
+
+// Permission represents access control rules
+type Permission struct {
+	ID        []byte `gorm:"type:BINARY(16);primaryKey"`
+	UserID    []byte `gorm:"column:userId;type:BINARY(16)"`
+	TokenID   []byte `gorm:"column:tokenId;type:BINARY(16)"`
+	OrgID     []byte `gorm:"column:orgId;type:BINARY(16);not null"`
+	AccountID []byte `gorm:"column:accountId;type:BINARY(16);not null"`
+	Type      uint   `gorm:"column:type;not null"`
+	Inserted  uint64 `gorm:"column:inserted;not null"`
+	Updated   uint64 `gorm:"column:updated;not null"`
+
+	User    User    `gorm:"foreignKey:UserID"`
+	Token   Token   `gorm:"foreignKey:TokenID"`
+	Org     Org     `gorm:"foreignKey:OrgID"`
+	Account Account `gorm:"foreignKey:AccountID"`
+}

models/price.go

@@ -0,0 +1,14 @@
+package models
+
+// Price represents currency exchange rates
+type Price struct {
+	ID       []byte  `gorm:"type:BINARY(16);primaryKey"`
+	OrgID    []byte  `gorm:"column:orgId;type:BINARY(16);not null"`
+	Currency string  `gorm:"column:currency;size:10;not null"`
+	Date     uint64  `gorm:"column:date;not null"`
+	Inserted uint64  `gorm:"column:inserted;not null"`
+	Updated  uint64  `gorm:"column:updated;not null"`
+	Price    float64 `gorm:"column:price;not null"`
+
+	Org Org `gorm:"foreignKey:OrgID"`
+}

models/session.go

@@ -0,0 +1,12 @@
+package models
+
+// Session represents user sessions
+type Session struct {
+	ID         []byte `gorm:"type:BINARY(16);primaryKey"`
+	Inserted   uint64 `gorm:"column:inserted;not null"`
+	Updated    uint64 `gorm:"column:updated;not null"`
+	UserID     []byte `gorm:"column:userId;type:BINARY(16);not null"`
+	Terminated uint64 `gorm:"column:terminated"`
+
+	User User `gorm:"foreignKey:UserID"`
+}

models/split.go

@@ -0,0 +1,17 @@
+package models
+
+// Split represents a single entry in a transaction
+type Split struct {
+	ID            uint   `gorm:"primaryKey;autoIncrement"`
+	TransactionID []byte `gorm:"column:transactionId;type:BINARY(16);not null"`
+	AccountID     []byte `gorm:"column:accountId;type:BINARY(16);not null"`
+	Date          uint64 `gorm:"column:date;not null"`
+	Inserted      uint64 `gorm:"column:inserted;not null"`
+	Updated       uint64 `gorm:"column:updated;not null"`
+	Amount        int64  `gorm:"column:amount;not null"`
+	NativeAmount  int64  `gorm:"column:nativeAmount;not null"`
+	Deleted       bool   `gorm:"column:deleted;default:false"`
+
+	Transaction Transaction `gorm:"foreignKey:TransactionID"`
+	Account     Account     `gorm:"foreignKey:AccountID"`
+}

models/token.go

@@ -0,0 +1,10 @@
+package models
+
+// Token represents an API token
+type Token struct {
+	ID        []byte `gorm:"type:BINARY(16);primaryKey"`
+	Name      string `gorm:"column:name;size:100"`
+	UserOrgID uint   `gorm:"column:userOrgId;not null"`
+
+	UserOrg UserOrg `gorm:"foreignKey:UserOrgID"`
+}

models/transaction.go

@@ -0,0 +1,18 @@
+package models
+
+// Transaction represents a financial transaction
+type Transaction struct {
+	ID          []byte `gorm:"type:BINARY(16);primaryKey"`
+	OrgID       []byte `gorm:"column:orgId;type:BINARY(16);not null"`
+	UserID      []byte `gorm:"column:userId;type:BINARY(16);not null"`
+	Date        uint64 `gorm:"column:date;not null"`
+	Inserted    uint64 `gorm:"column:inserted;not null"`
+	Updated     uint64 `gorm:"column:updated;not null"`
+	Description string `gorm:"column:description;size:300;not null"`
+	Data        string `gorm:"column:data;type:TEXT;not null"`
+	Deleted     bool   `gorm:"column:deleted;default:false"`
+
+	Org    Org     `gorm:"foreignKey:OrgID"`
+	User   User    `gorm:"foreignKey:UserID"`
+	Splits []Split `gorm:"foreignKey:TransactionID"`
+}

models/user.go

@@ -0,0 +1,21 @@
+package models
+
+// User represents a user account
+type User struct {
+	ID              []byte         `gorm:"type:BINARY(16);primaryKey"`
+	Inserted        uint64         `gorm:"column:inserted;not null"`
+	Updated         uint64         `gorm:"column:updated;not null"`
+	FirstName       string         `gorm:"column:firstName;size:50;not null"`
+	LastName        string         `gorm:"column:lastName;size:50;not null"`
+	Email           string         `gorm:"column:email;size:100;not null;unique"`
+	PasswordHash    string         `gorm:"column:passwordHash;size:100;not null"`
+	AgreeToTerms    bool           `gorm:"column:agreeToTerms;not null"`
+	PasswordReset   string         `gorm:"column:passwordReset;size:32;not null"`
+	EmailVerified   bool           `gorm:"column:emailVerified;not null"`
+	EmailVerifyCode string         `gorm:"column:emailVerifyCode;size:32;not null"`
+	SignupSource    string         `gorm:"column:signupSource;size:100;not null"`
+
+	UserOrgs []UserOrg `gorm:"foreignKey:UserID"`
+	Sessions []Session `gorm:"foreignKey:UserID"`
+	APIKeys  []APIKey  `gorm:"foreignKey:UserID"`
+}

models/user_org.go

@@ -0,0 +1,12 @@
+package models
+
+// UserOrg represents the relationship between users and organizations
+type UserOrg struct {
+	ID     uint   `gorm:"primaryKey;autoIncrement"`
+	UserID []byte `gorm:"column:userId;type:BINARY(16);not null"`
+	OrgID  []byte `gorm:"column:orgId;type:BINARY(16);not null"`
+	Admin  bool   `gorm:"column:admin;default:false"`
+
+	User User `gorm:"foreignKey:UserID"`
+	Org  Org  `gorm:"foreignKey:OrgID"`
+}