LCFS - Include an upload feature for the IDIR side to upload additional documents (In progress)

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**Purpose**
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**Acceptance Criteria**
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- [ ] second
- [ ] third

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The issue names no files, tests, or entry points, and its acceptance criteria are placeholders. Start by mapping the existing IDIR document workflow and upload handling, then confirm the intended scope with maintainers; done means concrete acceptance criteria are met and covered by relevant tests.

Written by the indexing model from the issue text.