fix(storage): exclude watch control files from backups

[wdsjjs]

Description

Fix backup and restore round trips when a workspace contains watch tasks.

ov backup previously included .watch_tasks.json and its temporary/backup variants, while restore correctly rejects these internal control files. This produced backup packages that could not be restored.

Watch control files are now excluded from backups. Restore-side validation remains unchanged.

Related Issue

Fixes #4139

Changes Made

• Exclude watch task control files from _backup_entries().
• Keep instance-local scheduler state out of portable backup packages.
• Add regression coverage to verify that the files are absent from both the archive and manifest, and that the backup can be restored.

Testing

PYTHONPATH=. .venv/bin/python -m pytest --no-cov \
  tests/misc/test_ovpack_import_policy.py -v

.venv/bin/ruff format --check \
  openviking/storage/ovpack/operations.py \
  tests/misc/test_ovpack_import_policy.py

.venv/bin/ruff check \
  openviking/storage/ovpack/operations.py \
  tests/misc/test_ovpack_import_policy.py

git diff --check

[hachimin-wh]

The backup-side exclusion is correct and the test covers the full
.watch_tasks.json / .bak / .tmp triple. One note from the issue author: this is
suggested fix 1 only — packs already produced on instances with watch tasks remain
unrestorable; suggested fix 2 (restore skips the control file with a log instead of failing
the whole pack) would recover them, which #4150 adds on top of the same backup change.