Refactor: Use doctate-common for shared logic

Moves shared types and utility functions to a new `doctate-common`
crate.
This includes:
- API key header constant
- AckResponse and AckStatus types
- Timestamp formatting and parsing utilities

This change centralizes common functionality, reducing duplication and
improving maintainability.
The `server` crate now depends on `doctate-common`.

server/src/routes/case_actions.rs

@@ -10,6 +10,8 @@ use time::OffsetDateTime;
 use tokio::io::AsyncWriteExt;
 use tracing::{info, warn};
 
+use doctate_common::timestamp::{filename_stem_to_recorded_at, now_rfc3339};
+
 use crate::analyze::{
     AnalysisInput, AnalyzeJob, AnalyzeSender, RecordingInput, ANALYSIS_INPUT_FILE, DOCUMENT_FILE,
 };
@@ -229,16 +231,6 @@ pub(crate) async fn write_input_create_new(
     Ok(())
 }
 
-/// Reverse the filesystem-safe timestamp mapping applied in `upload.rs`:
-/// `:` in the time portion was replaced with `-`. Split at `T`, undo hyphens
-/// only in the time part to avoid touching date hyphens.
-fn filename_stem_to_recorded_at(stem: &str) -> String {
-    match stem.split_once('T') {
-        Some((date, time)) => format!("{}T{}", date, time.replace('-', ":")),
-        None => stem.to_string(),
-    }
-}
-
 /// Read `case_dir/document.md`. Returns `None` if no document exists.
 pub(crate) async fn read_document(case_dir: &Path) -> Option<String> {
     tokio::fs::read_to_string(case_dir.join(DOCUMENT_FILE)).await.ok()
@@ -295,7 +287,7 @@ pub async fn handle_delete_case(
 
     let marker = DeleteMarker {
         batch: uuid::Uuid::new_v4(),
-        deleted_at: now_rfc3339()?,
+        deleted_at: now_rfc3339(),
     };
     write_delete_marker(&case_dir, &marker).await?;
 
@@ -444,28 +436,3 @@ async fn restore_batch(user_root: &Path, batch: uuid::Uuid) -> usize {
     }
     count
 }
-
-fn now_rfc3339() -> Result<String, AppError> {
-    OffsetDateTime::now_utc()
-        .format(&Rfc3339)
-        .map_err(|e| AppError::Internal(format!("format timestamp: {e}")))
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    #[test]
-    fn filename_stem_roundtrip() {
-        assert_eq!(
-            filename_stem_to_recorded_at("2026-04-15T10-32-00Z"),
-            "2026-04-15T10:32:00Z"
-        );
-        // Date-only hyphens are preserved.
-        assert_eq!(
-            filename_stem_to_recorded_at("2026-04-15T10-32-00.123Z"),
-            "2026-04-15T10:32:00.123Z"
-        );
-    }
-
-}

server/src/routes/upload.rs

@@ -2,6 +2,7 @@ use std::path::{Path, PathBuf};
 
 use axum::extract::{Multipart, State};
 use axum::Json;
+use doctate_common::timestamp::recorded_at_to_filename_stem;
 use tokio::sync::mpsc::error::TrySendError;
 use tracing::{info, warn};
 
@@ -72,7 +73,7 @@ pub async fn handle_upload(
     let case_dir = resolve_case_dir(&user.data_dir, &case_id).await?;
 
     // Build a filesystem-safe filename from the timestamp (colons → hyphens).
-    let safe_timestamp = recorded_at.replace(':', "-");
+    let safe_timestamp = recorded_at_to_filename_stem(&recorded_at);
     let file_path = case_dir.join(format!("{safe_timestamp}.m4a"));
 
     tokio::fs::write(&file_path, &audio).await?;