fix(sync): surface attachment/folder restore failures (audit 2.3)

applyRemoteSnapshot swallowed attachment + folder restore errors in silent
catch blocks. Count them (attFailed/folderFailed) and warn in a toast after
the sync summary. These don't abort the push (the entry synced, only its
attachment/folder didn't) unlike a failed entry import.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

js/app.sync.js

@@ -273,8 +273,8 @@ async function buildSyncSnapshot() {
 }
 
 async function applyRemoteSnapshot(remote) {
-    if (!remote || !Array.isArray(remote.entries)) return { added:0, updated:0, deleted:0, failed:0 };
-    let added = 0, updated = 0, deleted = 0, failed = 0;
+    if (!remote || !Array.isArray(remote.entries)) return { added:0, updated:0, deleted:0, failed:0, attFailed:0, folderFailed:0 };
+    let added = 0, updated = 0, deleted = 0, failed = 0, attFailed = 0, folderFailed = 0;
 
     // Ensure state.entries reflects the live DB before we read updated_at
     // for the resurrection arbitration below — a restore-then-sync must
@@ -356,7 +356,7 @@ async function applyRemoteSnapshot(remote) {
                         name: f.name, color: f.color || '', icon: f.icon || '',
                     }),
                 });
-            } catch (_) {}
+            } catch (_) { folderFailed++; }
         }
         await loadFolders();
     }
@@ -410,7 +410,7 @@ async function applyRemoteSnapshot(remote) {
                                     size_bytes:     a.size_bytes || bytes.length,
                                 }),
                             });
-                        } catch (_) {}
+                        } catch (_) { attFailed++; }
                     }
                 }
             } catch (_) { failed++; }
@@ -432,7 +432,7 @@ async function applyRemoteSnapshot(remote) {
             } catch (_) { failed++; }
         }
     }
-    return { added, updated, deleted, failed };
+    return { added, updated, deleted, failed, attFailed, folderFailed };
 }
 
 // Update the inline sync-status label next to the button. Empty string
@@ -623,5 +623,15 @@ async function runSyncNow(_attempt) {
         'pushed ' + pushedCount + ' ' +
         (pushedCount === 1 ? 'entry' : 'entries');
     toast('Sync complete — ' + summary);
+
+    // Surface additive-restore gaps that used to be swallowed silently
+    // (§2.3). These don't risk overwriting the remote — the entry synced,
+    // only its attachment/folder didn't come down — so they warn, not abort.
+    if (merged.attFailed || merged.folderFailed) {
+        const parts = [];
+        if (merged.attFailed)    parts.push(merged.attFailed + ' attachment(s)');
+        if (merged.folderFailed) parts.push(merged.folderFailed + ' folder(s)');
+        toast(parts.join(' · ') + ' failed to sync — retry sync', 'warning');
+    }
 }