attachments sync: attach offline, upload when linked, removals stick (#5168)

Desktop could not create an attachment at all, and a removed attachment or
dismissed preview came back on the next pull. Now:

- core: add_attachment keeps the bytes in the blob store and queues the row
  (schema v10: attachments.uploaded / upload_error). Push uploads it once its
  note has landed. A refusal that retrying won't fix (too large, id clash, hash
  mismatch) is recorded on the file and not re-sent every cycle; the editor
  shows it.
- core: removing a synced attachment or dismissing a preview leaves a tombstone
  in pending_deletes; push sends it as an `attachment`/`preview` delete, and a
  pull while it waits doesn't put the row back. A pull also keeps files still
  waiting to upload instead of replacing them wholesale.
- server: PUT /api/sync/attachments/<id> (raw body, sha256-checked, idempotent,
  size-capped) and child deletes in push, which apply regardless of LWW and
  answer noop for rows the caller can't see. One store_attachment helper for
  the upload route, the importer and sync. Protocol 5, feature attachment_sync;
  the client sends neither to a server without it.
- server: migration 0031 makes a link preview's insert/delete bump its note, so
  background-fetched previews and web dismissals reach linked devices.
- desktop: Attach and paste-image work offline (raw-bytes IPC command).
- SVG is served as a download by the desktop blob scheme too (as #1981 did for
  the web), and drawn as a file chip on both.
- autosync: drop the catch_unwind; release builds abort on panic, so it only
  ever worked in debug builds.

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

desktop/src-tauri/src/autosync.rs

@@ -270,18 +270,17 @@ fn worker(app: AppHandle, rx: Receiver<Request>) {
 
         let blobs = app.state::<BlobStore>();
         let started = Instant::now();
-        // A panic inside one cycle must not end automatic sync for the rest of the
-        // session: this thread is the only thing that runs it, and a dead thread
-        // looks exactly like a quiet one. It becomes a failed cycle instead.
-        let result = std::panic::catch_unwind(std::panic::AssertUnwindSafe(|| {
-            tauri::async_runtime::block_on(engine::run_cycle(
-                db.inner(),
-                blobs.inner(),
-                &base_url,
-                &token,
-            ))
-        }))
-        .unwrap_or_else(|_| Err("The sync cycle crashed; it will be retried.".to_string()));
+        // No catch_unwind here, and that is deliberate. The workspace's release profile
+        // sets `panic = "abort"`, so a panic in a cycle ends the whole app rather than
+        // this thread, and a catch would only ever work in a debug build. What
+        // matters is that the worker can't die silently and leave the app looking
+        // synced, and an abort is anything but silent.
+        let result = tauri::async_runtime::block_on(engine::run_cycle(
+            db.inner(),
+            blobs.inner(),
+            &base_url,
+            &token,
+        ));
         pace.last_attempt = Some(started);
         // Whatever is still pending after this cycle is not new on the next tick.
         pace.sent = pending(&db);