Optimize showtime requests and theater lookup

[tducret]

Summary

• stop querying additional dates when a theater has no showtimes
• jump directly to the next available showtime date when Allocine provides one
• resolve theater details from page metadata when the showtime API has no current results
• cover these behaviors with recorded VCR responses and snapshots

Validation

• uv run pytest -q
• uv run ruff check allocine/client.py tests/test_allocine.py
• uv run ruff format --check allocine/client.py tests/test_allocine.py
• uv run ty check
• uv run seances W1021 --semaine