fix: close leaked file handle in orgnode parser

[buley]

Summary

src/khoj/processor/content/org_mode/orgnode.py:57 opens a file with open(filename, "r") but never closes it. The file handle leaks for the lifetime of the returned Orgnode list.

Fix

Replaced bare open() with a with statement to ensure the file is closed after makelist() finishes reading.

# Before
def makelist_with_filepath(filename):
    f = open(filename, "r")
    return makelist(f, filename)

# After
def makelist_with_filepath(filename):
    with open(filename, "r") as f:
        return makelist(f, filename)

This is safe because makelist() fully consumes the file during the call (building the Orgnode list from file contents), so the file handle is no longer needed after it returns.