- Remove Python 3.9 and PyPy 3.9 from test matrix
- Add Python 3.14 and PyPy 3.10 to test matrix

The thread-based timeout method causes pytest-xdist workers to crash on
Ubuntu. Let pytest-timeout automatically choose the best method: signal
on Unix (compatible with multiprocessing) and thread on Windows (where
signals aren't available).

The 1.5MB MP4 binary file causes pytest-xdist workers to crash on Windows
when chardet attempts to detect its encoding. This is specific to Windows
and the interaction between pytest-xdist's multiprocessing and large binary
file processing.

Solution: Skip the MP4 test specifically on Windows (sys.platform == 'win32').
This allows all other binary file tests (PNG, GIF, JPG, XLSX, WEBP) to run
normally while avoiding the crash.

Two tests were causing timeouts:

1. MP4 file (tests/None/sample-1.mp4): The 1.5MB binary file times out
   on all platforms, not just Windows. Extended the skip to all platforms.

2. Hebrew XML file (tests/windows-1255-hebrew/hydepark.hevre.co.il.7957.xml):
   This file causes a timeout in the remove_xml_tags function, likely due to
   performance issues with large files containing many XML tags. Skip this
   test for now - the underlying performance issue needs investigation.

Both tests now skip with appropriate messages to avoid CI failures.

The previous approach of skipping tests was wrong. The real issue was:

1. Per-function timeout of 10 seconds was too aggressive for larger files
   (1.5MB MP4, 80KB XML) on CI runners with pytest-xdist overhead

2. timeout_func_only=true with thread method doesn't work well with
   pytest-xdist's multiprocessing

Solution:
- Increase default timeout from 30s to 60s
- Remove timeout_func_only setting (defaults to False)
- Remove per-test @pytest.mark.timeout(10) decorator
- This allows pytest-timeout to use signal method (Unix) which works
  properly with multiprocessing

Now all tests run without skipping, with adequate timeout for CI overhead.