Introduce a "Back to Cases" button in the document view and update the
case detail page to conditionally display the "Analyze" button. Also,
add a copy-to-clipboard functionality for the document content.
Introduce a `DocumentTemplate` struct for rendering the document view,
replacing inline HTML.
Introduce a `CaseFlags` struct to encapsulate the logic for determining
various UI states of a case (e.g., `has_document`, `analyzing`,
`can_close`, `llm_missing`).
Update `handle_case_detail` to use `compute_flags` for populating the
`CaseDetailTemplate`.
Update `scan_user_cases` to compute `analyzing` and `has_document` flags
for the `UserCaseView`.
Add new template logic in `case_detail.html` to display actions based on
`CaseFlags`.
Add new template logic in `my_cases.html` to display `analyzing` and
`done-doc` labels for cases.
Create a new `document.html` template.
Add a helper function `any_document_exists` to check for the presence of
a document file.
Brummel