(WIP) Implement Generics API

[jinzhu]

feat(gorm): add generic CRUD & query interfaces

This commit introduces a type-safe, generic API layer on top of GORM that
allows you to perform Create, Read, Update, Delete and raw SQL operations

Helper constructor:

  func G[T any](db *DB, opts ...clause.Expression) Interface[T]

Basic usage:

// Create a user
u := User{Name: "Alice"}
if err := gorm.G[User](DB).Create(ctx, &u); err != nil {
  // handle error
}

// Query by name and count
cnt, err := gorm.G[User](DB).
  Where("name = ?", "Alice").
  Count(ctx, "*")

// Raw + Find
users, err := gorm.G[User](DB).
  Raw("SELECT * FROM users WHERE created_at > ?", since).
  Find(ctx)

// Update one field
rows, err := gorm.G[User](DB).
  Where("id = ?", u.ID).
  Update(ctx, "email", "alice@example.com")

// Delete
deleted, err := gorm.G[User](DB).
  Where("id = ?", u.ID).
  Delete(ctx)