enh: rework form resubmit via self-dispatch rather than a network-call

[lprimak]

Internals of data loss prevention / data save functionality is redone without a network call.
Ran security model tests with LLMs, with only improvements reported (no regressions)

TODO: update docs on the website.

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[lprimak]

For now, this is full of AI slop, but it (at least tests pass) works?. Needs lots of refactoring and simplification, so the code actually makes some sense

[lprimak]

Got rid of lots of AI slop for now, time for real review and manual refactoring.

[lprimak]

Code review complete. Slop removed. Test/docs added.

Need lots of manual testing, which is up next.

[lprimak]

Ran in production for a few days, no regressions found, functionality works in real applications.