feature: CCP-4997 Implement Offline Submission Queue and Sync

[gary-jipp]

Description

Type of Change

feat (a new feature)

What this PR adds

• Per-form opt-in: form designers enable "offline submission" on a form.
• Offline submit: when a user submits while offline, the submission is saved in the browser instead of failing.
• Auto-sync on reconnect: queued submissions are sent to the server automatically when the user is back online, with a progress dialog showing each one's status.
• Pending list: users can see what's queued, add an optional note when queuing, and discard entries they no longer want.
• Designer simulation: a small "Online" / "Simulating Offline" toggle chip lets designers preview the whole offline flow on a published form without actually disconnecting.
• Safe replays: server-side dedup so a flaky network can't create duplicate submissions.

Checklist

• I have read the CONTRIBUTING doc
• I have checked that unit tests pass locally with my changes
• I have run the npm script lint on the frontend and backend
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)
• I have approval from the product owner for the contribution in this pull request

Further comments

[github-actions]

Coverage Report (Application)

Totals
Statements:	78.27% ( 9057 / 11572 )
Methods:	76.9% ( 962 / 1251 )
Lines:	80.93% ( 5540 / 6845 )
Branches:	73.5% ( 2555 / 3476 )

[github-actions]

Coverage Report (Frontend)

Totals
Statements:	68.29% ( 10690 / 15653 )
Methods:	61.98% ( 1842 / 2972 )
Lines:	73.97% ( 5943 / 8034 )
Branches:	62.51% ( 2905 / 4647 )

[sonarqubecloud]

Quality Gate passed

Issues
6 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[github-actions]

Release cd9fe03 deployed at https://chefs-dev.apps.silver.devops.gov.bc.ca/pr-1916