Generated images survive moves and renames

Agents tidy up folders after generating images (sort into subfolders, rename
revisions); the image records kept the old path, so /api/images/<id>/file
answered 404 and only the requesting device still showed them from its cache.

- Generated images get a copy in the image store (images.blob, kept by the
  blob GC); existing ones are copied once on start-up.
- Records follow: after bash commands with mv/rename (missing images of the
  owner from the last two weeks, found by name or by content hash), when moved
  with the file manager (file or folder), and on access (served from the copy,
  relocated in the background; without a copy found by file name).
- Chat gallery falls back to the preview the model saw when the file is gone.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

server/src/api.rs

@@ -1563,13 +1563,26 @@ fn own_image(app: &App, user: &User, id: &str) -> Result<crate::store::ImageReco
 
 async fn image_file(Extension(user): Extension<User>, State(app): State<AppState>, Path(id): Path<String>) -> Result<Response, ApiError> {
     let img = own_image(&app, &user, &id)?;
-    let bytes = tokio::fs::read(&img.path).await.map_err(|_| not_found("image file"))?;
-    let ctype = match std::path::Path::new(&img.path).extension().and_then(|e| e.to_str()) {
+    let ctype_of = |p: &str| match std::path::Path::new(p).extension().and_then(|e| e.to_str()).map(|e| e.to_ascii_lowercase()).as_deref() {
         Some("jpg") | Some("jpeg") => "image/jpeg",
         Some("webp") => "image/webp",
         _ => "image/png",
     };
-    Ok(([(axum::http::header::CONTENT_TYPE, ctype), (axum::http::header::CACHE_CONTROL, "private, max-age=86400")], bytes).into_response())
+    let respond = |ctype: String, bytes: Vec<u8>| ([(axum::http::header::CONTENT_TYPE, ctype), (axum::http::header::CACHE_CONTROL, "private, max-age=86400".to_string())], bytes).into_response();
+    if let Ok(bytes) = tokio::fs::read(&img.path).await {
+        return Ok(respond(ctype_of(&img.path).into(), bytes));
+    }
+    // The file was moved or renamed (agents tidy up folders): with a copy in the image store,
+    // answer from there and look for the file in the background; otherwise look now.
+    if let Some((mime, bytes)) = img.blob.as_deref().map(|h| app.store.blob(h)).transpose()?.flatten() {
+        let a = app.clone();
+        tokio::task::spawn_blocking(move || crate::images::relocate(&a, &img));
+        return Ok(respond(mime, bytes));
+    }
+    let a = app.clone();
+    let found = tokio::task::spawn_blocking(move || crate::images::relocate(&a, &img)).await.ok().flatten().ok_or_else(|| not_found("image file"))?;
+    let bytes = tokio::fs::read(&found).await.map_err(|_| not_found("image file"))?;
+    Ok(respond(ctype_of(&found.display().to_string()).into(), bytes))
 }
 
 async fn delete_image(Extension(user): Extension<User>, State(app): State<AppState>, Path(id): Path<String>) -> ApiResult {