feat: Support FETCH FIRST/OFFSET (SQL:2008 standard pagination)

[ajitpratap0]

Description

Add support for SQL:2008 standard pagination syntax as alternative to LIMIT/OFFSET.

Example SQL

-- FETCH FIRST
SELECT * FROM users ORDER BY id FETCH FIRST 10 ROWS ONLY;
SELECT * FROM products FETCH FIRST 5 ROW ONLY;

-- With OFFSET
SELECT * FROM users ORDER BY id OFFSET 20 ROWS FETCH NEXT 10 ROWS ONLY;

-- Percentage
SELECT * FROM users FETCH FIRST 10 PERCENT ROWS ONLY;

-- WITH TIES
SELECT * FROM products ORDER BY price FETCH FIRST 5 ROWS WITH TIES;

Current Behavior

LIMIT/OFFSET works but SQL standard FETCH FIRST syntax is not supported.

Expected Behavior

Parser should recognize FETCH FIRST/NEXT and OFFSET ROWS as pagination clauses.

Priority

Medium - SQL standard compliance

Implementation Notes

• Add tokens: FETCH, FIRST, NEXT, ROWS, ROW, ONLY, TIES, PERCENT
• Add FetchClause to SelectStatement AST
• Support WITH TIES for including ties in ordered results