feat: CREATE TABLE LIKE source_table

[tianzhou]

Fix #13

[Copilot]

Pull Request Overview

This PR adds support for CREATE TABLE LIKE statements in PostgreSQL schema management. It enables tables to inherit structure from existing tables using the LIKE clause with various options (INCLUDING ALL, INCLUDING DEFAULTS, etc.).

• Implements parsing and expansion of CREATE TABLE LIKE clauses
• Adds support for copying columns, constraints, indexes, and comments from source tables
• Generates appropriate DDL that expands LIKE clauses into explicit column definitions

Reviewed Changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 2 comments.

File	Description
internal/ir/parser.go	Adds constants, parsing logic, and expansion functionality for LIKE clauses
internal/ir/ir.go	Defines LikeClause struct and adds LikeClauses field to Table
internal/diff/table.go	Updates DDL generation to handle LIKE clauses in CREATE TABLE statements
testdata files	Test data showing expected behavior for CREATE TABLE LIKE expansion

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