fix: properly strip line comments and convert tabs to spaces in sqlparse.format

[label-hook]

Summary

Fixes two issues in sqlparse.format() when using strip_comments=True and reindent=True:

1. Line comments starting with -- were not being properly removed
2. Tabs were not being converted to spaces during reindentation

Closes #16

Changes

StripCommentsFilter (sqlparse/filters/others.py)

• Fixed the _process method to properly identify and remove line comments (--)
• Enhanced comment detection logic to handle line comments that appear after SQL code on the same line
• Preserved newlines and statement structure while removing comment content

ReindentFilter (sqlparse/filters/reindent.py)

• Added tab-to-space conversion in the reindentation process
• Modified the _process method to normalize tabs to spaces before applying indentation
• Ensures consistent spacing when reindent=True is used

Testing

• Created comprehensive test cases covering both line comment removal and tab conversion
• Tested with the original issue.sql file to verify both problems are resolved
• Verified that strip_comments=True now properly removes all -- comments
• Confirmed that reindent=True converts tabs to spaces for consistent indentation
• All existing tests continue to pass, ensuring no regression in functionality

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Closes #16