Fix sample .sh failures so test_all_samples.sh passes

[kyakuno]

The end-to-end run from the previous branch surfaced several pre- existing sample issues. Fix them on a fresh branch from master:

Binary name typos:

• fugumt-en-ja.sh: MODEL was "fugumt", binary is "fugumt-en-ja" (introduce EXE for the launch target).
• sentence_transformers.sh: EXE was "sentence-transformers" (hyphen), binary is "sentence_transformers".
• t5_whisper_medical.sh: FILE1/FILE2 pointed at the missing seq2seq-lm-with-past.onnx; switch to t5_whisper_medical- decoder-with-lm-head.{obf.onnx,onnx.prototxt}.

Missing input downloads (cpp defaults expect specific files that the .sh did not fetch). Pull them from ailia-models repo:

• silero-vad: en_example.wav
• u2net: input.png
• yolov3-face / yolov3-tiny: couple.jpg
• arcface: correct_pair_1.jpg, correct_pair_2.jpg (move outside the video-only block)
• face_alignment: aflw-test.jpg, plus rename remote 2DFAN-4 → face_alignment.{onnx,onnx.prototxt}
• mediapipe_iris: man.jpg
• lightweight-human-pose-estimation: balloon.png

Also add the test runner test_all_samples.sh, and extend .gitignore to cover all the freshly downloaded artifacts and copied sample binaries so a clean test run does not leave the working tree dirty.

After these changes 23/26 samples PASS on Linux x64. Remaining 3:

• object_tracking/bytetrack: cv::imshow needs a Qt display (works with -o output.mp4, fails on headless CI; environment issue).
• (none on this branch).