[19.0][MIG] web_calendar_slot_duration: Migration to 19.0

[tishmen]

Scope

• web_calendar_slot_duration only (OCA/web)

Summary

• Migrate to Odoo 19 using the working feature branch code.
• Context handling aligned with 19.0.
• Asset paths are relative under web.assets_backend.

Pre-commit

• Verified locally; no additional changes applied here to keep parity with the feature branch.

Tests Command: ./odoo/odoo-bin -c odoo.conf -d odoo_calendar_tests_web_slot_001 -i web_calendar_slot_duration --test-enable --test-tags "/web_calendar_slot_duration" --log-level=info --stop-after-init Result: module installs cleanly (no tests in addon).

[tishmen]

Supersedes #3306 to preserve history per OCA 19.0 migration process.

[pedrobaeza]

/ocabot migration web_calendar_slot_duration