Add markdown rendering for LLM output

This commit introduces a new module `analyze::render` to handle the
rendering of Markdown content produced by the LLM into safe HTML.

The LLM output now includes a custom `==text==` highlighting convention
to indicate sections that require doctor review due to potential
transcription errors or incomplete information. This highlighting is
converted into `<mark>` tags in the final HTML.

To ensure security, all LLM-generated Markdown is first HTML-escaped.
This prevents any malicious HTML or script injection from being executed
in the browser. Only the custom `<mark>` tags are preserved as
functional HTML elements.

The process is as follows:
1.  The raw Markdown from the LLM is processed.
2.  All HTML special characters (`<`, `>`, `&`, `"`, `'`) are escaped.
3.  The `==text==` highlights are replaced with `<mark>text</mark>`.
4.  The resulting string is parsed as Markdown by `pulldown-cmark`.
5.  The parsed Markdown is converted to HTML, which is then safe to
    inject into the Askama template using the `|safe` filter.

The `Cargo.toml` and `Cargo.lock` files have been updated to include the
`pulldown-cmark` dependency. The `document.html` template has been
modified to use a `div` with the class `doc-content` instead of a `pre`
tag, allowing the rendered HTML to be displayed correctly. The
`handle_document_view` function now calls the new `md_to_html` rendering
function.

server/Cargo.lock

@@ -339,6 +339,7 @@ dependencies = [
  "axum-extra",
  "bcrypt",
  "dotenvy",
+ "pulldown-cmark",
  "rand 0.8.5",
  "reqwest",
  "rpassword",
@@ -1150,6 +1151,24 @@ dependencies = [
  "unicode-ident",
 ]
 
+[[package]]
+name = "pulldown-cmark"
+version = "0.13.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7c3a14896dfa883796f1cb410461aef38810ea05f2b2c33c5aded3649095fdad"
+dependencies = [
+ "bitflags",
+ "memchr",
+ "pulldown-cmark-escape",
+ "unicase",
+]
+
+[[package]]
+name = "pulldown-cmark-escape"
+version = "0.11.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "007d8adb5ddab6f8e3f491ac63566a7d5002cc7ed73901f72057943fa71ae1ae"
+
 [[package]]
 name = "quinn"
 version = "0.11.9"
@@ -1202,7 +1221,7 @@ dependencies = [
  "once_cell",
  "socket2",
  "tracing",
- "windows-sys 0.52.0",
+ "windows-sys 0.59.0",
 ]
 
 [[package]]