Add declarative LITEFile filing handoff

[nonprofittechy]

The Vermont RFA interview can now hand its completed answers and four enabled court PDFs to LITEFile as an editable filing draft. This is the Docassemble sender half of SuffolkLITLab/LITEFile#106.

Companion receiver PR: SuffolkLITLab/LITEFile#225.

All interview-specific behavior is visible in litefile.yml: jurisdiction and filing intent, known case facts, party roles, semantic filing hints, and the document map. The Python module is interview-independent transport code so it can move into a shared integration package later. The main interview only includes the YAML and displays its button on the download screen.

The adapter uses the flat server-wide litefile configuration, defaults litefile_person() to normal AssemblyLine/Docassemble individual fields through showifdef, retains AssemblyLine's cache and DAFile handles for idempotent retries, and uploads with BackgroundAction. Its initial routing block reliably consumes the result after Docassemble's wait refresh. Background task arguments are empty, so filing answers, correction tokens, and credentials are not copied into task arguments.

A separate follow-up commit adds declarative litefile_filing_hint_overrides. Authors can replace general semantic hints by county and then by court, including per-document filing type, document type, and filing component hints.

Validation:

• python -I -m pytest -q tests/test_litefile.py — 17 passed.
• Ruff and whitespace checks passed.
• Installed with ~/venv/bin/dainstall --server localhost ..
• A completed synthetic adult RFA session generated and transferred four actual court PDFs; the instructions PDF stayed out of the court bundle.
• The one-click BackgroundAction flow created a draft and displayed its success screen.
• Retrying returned HTTP 200 while retaining one receipt, one draft, four documents, and the same source identity.
• The final installed pass sent the default empty county/court override maps and created another four-document draft successfully.
• Earlier authorized dev validation used a real Vermont account and completed fee review and one submission. The quoted fee was $14.40 and all four filing statuses were confirmed submitted. The dev EFSP stand-in PDF setting was active.

No production configuration or credentials are included in this branch.

[nonprofittechy]

This package has some files that would move into a dedicated standalone repo if the shape of this all looks good.