fix: settle silent-only cases to Empty oneliner state

Introduce `TranscriptState { Pending, Silent, Content }` in
doctate-common as the canonical three-way state of a recording's
`.transcript.txt` sidecar. Previously each call-site projected the
raw `Option<String>` / `.exists()` onto its own 2-state view and the
projections disagreed: the UI treated a 0-byte silent transcript like
`Content` while the oneliner worker treated it like `Pending`,
leaving silent-only cases stuck on "generiere Titel …" forever with
no persisted oneliner.json.

`update_oneliner` now settles a silent-only case to
`OnelinerState::Empty` when no `Content` transcript exists and no
recording is still `Pending`, so the UI resolves to "unbenannt" and
recovery treats it as terminal.

Single reader: `paths::read_transcript_state`. All call-sites
(scan_recordings, compute_oneliner_display, has_pending_recordings,
all_transcripts_joined, read_recordings, enqueue_pending_for_user,
scan_m4as, cases_needing_oneliner_in, case_recordings.html) go
through the same typed abstraction and must handle `Silent` via
exhaustive match.

Regression tests:
- silent_case_empty_test: heal path settles silent-only case to
  Empty without calling Ollama
- case_page_silent_only_shows_empty_not_generating: UI renders
  "unbenannt", not "generiere Titel …"

server/src/routes/user_web.rs

@@ -5,6 +5,7 @@ use std::sync::atomic::Ordering;
 use askama::Template;
 use axum::extract::{Query, State};
 use axum::response::Html;
+use doctate_common::TranscriptState;
 use doctate_common::oneliners::OnelinerState;
 use serde::Deserialize;
 use tracing::{info, warn};
@@ -258,7 +259,7 @@ async fn compute_flags(
 
     let non_failed: Vec<&RecordingView> = recordings.iter().filter(|r| !r.failed).collect();
     let all_transcribed =
-        !non_failed.is_empty() && non_failed.iter().all(|r| r.transcript.is_some());
+        !non_failed.is_empty() && non_failed.iter().all(|r| r.transcript.has_file());
 
     let analyzable = !analyzing && all_transcribed;
 
@@ -486,7 +487,10 @@ pub async fn handle_case_page(
     let flags = compute_flags(&case_dir, &recordings, config.llm_configured(), a_busy).await;
 
     let recordings_count = recordings.len();
-    let transcribed_count = recordings.iter().filter(|r| r.transcript.is_some()).count();
+    let transcribed_count = recordings
+        .iter()
+        .filter(|r| r.transcript.has_file())
+        .count();
     let case_id_short = case_id_str.chars().take(8).collect();
     let is_admin = user.is_admin();
 
@@ -732,7 +736,7 @@ async fn compute_case_view(
         && recordings
             .iter()
             .filter(|r| !r.failed)
-            .all(|r| r.transcript.is_some());
+            .all(|r| r.transcript.has_file());
 
     let oneliner = compute_oneliner_display(case_path, &recordings).await;
 
@@ -809,7 +813,7 @@ async fn compute_oneliner_display(
         && recordings
             .iter()
             .filter(|r| !r.failed)
-            .all(|r| r.transcript.is_some());
+            .all(|r| r.transcript.has_file());
     let (state, _) = paths::read_oneliner_state(case_dir).await;
 
     if non_failed_count == 0 {