feat: Add case closing and document viewing routes

Adds API endpoints for closing a case, which triggers an analysis job,
and for viewing the generated document.

This also includes:
- New `AppError` variants: `Conflict` and `ServiceUnavailable`.
- Helper functions for file handling, date parsing, and document
  searching.
- Unit tests for helper functions.

server/src/routes/mod.rs

@@ -1,9 +1,10 @@
+mod case_actions;
 mod debug;
 mod health;
 mod login;
 mod upload;
+pub(crate) mod user_web;
 pub(crate) mod web;
-mod user_web;
 
 use axum::routing::{get, post};
 use axum::Router;
@@ -19,6 +20,14 @@ pub fn api_router() -> Router<AppState> {
         .route("/web/logout", post(login::handle_logout))
         .route("/web/cases", get(user_web::handle_my_cases))
         .route("/web/cases/{case_id}", get(user_web::handle_case_detail))
+        .route(
+            "/web/cases/{case_id}/close",
+            post(case_actions::handle_close_case),
+        )
+        .route(
+            "/web/cases/{case_id}/document",
+            get(case_actions::handle_document_view),
+        )
         .route("/web/", get(web::handle_case_list))
         .route(
             "/web/audio/{user}/{case_id}/{filename}",