[FIX] dms: complete Odoo 19 migration fixes

[Erp4759]

Follow-up fixes for OCA#475.

Changes:

• preserve directory/file defaults when Odoo 19 strips default_* context keys during contextual navigation
• use Odoo 19 Domain objects for computed-field search methods
• keep date-only rendering compatible with Odoo 19 views
• add regressions for read-only permissions and restricted direct binary URLs
• test real multipart upload and download

Validation:

• all pre-commit hooks pass
• fresh Odoo 19 install passes
• 68 test methods / 82 checks, 0 failures and 0 errors
• module upgrade passes

The branch is based directly on the current OCA migration PR head (171bd86), so it preserves the migrated history and contains one focused additional commit.