feat: Mark failed recordings with .m4a.failed

Add a new `failed` field to `RecordingView` and corresponding logic in
the worker.
When FFmpeg remuxing or Whisper transcription fails, the worker now
renames the
original `.m4a` file to `.m4a.failed`. This prevents the recovery scan
from
reprocessing these files and signals to the UI that transcription
failed.

The UI displays a message indicating failure and suggests renaming the
file
back to `.m4a` to retry. A new integration test
`worker_renames_audio_to_failed_on_whisper_error`
is included to verify this behavior.

server/tests/transcribe_test.rs

@@ -1,11 +1,14 @@
 use std::path::PathBuf;
 use std::time::Duration;
 
+use std::collections::HashMap;
+use std::sync::Arc;
+
+use doctate_server::config::{Config, User, WhisperUserSettings};
 use doctate_server::transcribe;
 use doctate_server::transcribe::ffmpeg::remux_faststart;
 use doctate_server::transcribe::ollama::{generate_oneliner, OllamaError};
 use doctate_server::transcribe::recovery::scan_and_enqueue;
-use doctate_server::config::WhisperUserSettings;
 use doctate_server::transcribe::whisper::{transcribe, WhisperError};
 use serde_json::json;
 use wiremock::matchers::{body_partial_json, method, path, query_param};
@@ -242,6 +245,75 @@ async fn recovery_enqueues_only_pending_recordings() {
     assert!(received[1].ends_with("2026-04-12T10-00-00Z.m4a"));
 }
 
+// -------------------- Worker: failure marker --------------------
+
+fn test_config_with_whisper(whisper_url: String) -> Arc<Config> {
+    Arc::new(Config {
+        server_port: 3000,
+        data_path: "/tmp".into(),
+        log_level: "info".into(),
+        log_path: "/tmp".into(),
+        log_max_days: 90,
+        users: vec![User {
+            slug: "dr_test".into(),
+            api_key: "k".into(),
+            web_password: "unused".into(),
+            role: "doctor".into(),
+            whisper: Default::default(),
+        }],
+        api_keys: HashMap::new(),
+        retention_audio_days: 30,
+        retention_transcript_days: 30,
+        retention_document_days: 0,
+        whisper_url,
+        whisper_timeout_seconds: 5,
+        // Ollama URL is irrelevant — worker never reaches it in the failure path.
+        ollama_url: "http://127.0.0.1:1".into(),
+        ollama_model: "test".into(),
+        ollama_keep_alive: 0,
+        llm_url: String::new(),
+        llm_api_key: String::new(),
+        llm_model: String::new(),
+        llm_temperature: 0.0,
+        session_timeout_hours: 8,
+    })
+}
+
+#[tokio::test]
+async fn worker_renames_audio_to_failed_on_whisper_error() {
+    let server = MockServer::start().await;
+    Mock::given(method("POST"))
+        .and(path("/asr"))
+        .respond_with(ResponseTemplate::new(500).set_body_string("boom"))
+        .mount(&server)
+        .await;
+
+    // Real case dir with a real m4a fixture so ffmpeg remux succeeds.
+    let tmp = tempfile::tempdir().unwrap();
+    let case_dir = tmp.path().join("dr_test/open/aaaa");
+    std::fs::create_dir_all(&case_dir).unwrap();
+    let audio = case_dir.join("2026-04-13T10-30-00Z.m4a");
+    std::fs::copy(fixture("sample.m4a"), &audio).unwrap();
+
+    let config = test_config_with_whisper(server.uri());
+    let (tx, rx) = transcribe::channel();
+    tx.send(transcribe::TranscribeJob {
+        audio_path: audio.clone(),
+        user_slug: "dr_test".into(),
+    })
+    .await
+    .unwrap();
+    drop(tx); // close channel so the worker loop exits after processing the job
+
+    let client = reqwest::Client::new();
+    transcribe::worker::run(rx, config, client).await;
+
+    // Audio must have been renamed so recovery skips it next time.
+    assert!(!audio.exists(), "original .m4a still present");
+    let failed = case_dir.join("2026-04-13T10-30-00Z.m4a.failed");
+    assert!(failed.exists(), "expected {} to exist", failed.display());
+}
+
 // -------------------- Ollama client --------------------
 
 const MODEL: &str = "gemma3:4b";