Add type-safe Go code generation from migration schema

[ljluestc]

- What I did
Implemented a goose generate command to generate type-safe Go code from SQL queries in a queries/ directory, using schema information from migration files. Supports read-only (pgx/v5) and read/write (sql/db) queries with basic dynamic query support.

- How I did it

• Added generate command in cmd/goose/main.go with flags -dir, -queries, and -out.
• Created internal/parser/schema.go to parse CREATE TABLE statements for schema inference.
• Implemented internal/generator/generator.go to generate type-safe Go code using templates, with parameter inference for dynamic queries.
• Updated goose.go to integrate parsing and generation.
• Supported read-only vs. read/write queries via _read naming convention.
• Used sql/db for write operations and pgx/v5 for read-only queries.