fix(jobs): flush the checkpoint tail, so progress reflects reality

All three import jobs only checkpointed on a full batch, so the
remainder after the last one was never counted. A run shorter than
BATCH_SIZE never checkpointed at all: `scanned_count` stayed 0 against
a known `total_rows`, and the admin progress bar sat at zero for the
whole run and finished there.

Seen on a transcode_import run over 20 entries — 13 imported, 5
negatives, 2 already present, progress 0/20 throughout. The thumbnail
imports had it too, just less visibly: a 105-file run reported
`scanned_count: 100`, losing the tail rather than all of it.

Cursor-wise the final checkpoint is a no-op — the walk is finished, so
nothing resumes from it — but the scanned delta is what the progress
display reads, and it has to include the last partial batch.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/infrastructure/services/transcode_import_service.rs

@@ -253,6 +253,8 @@ impl RecoverableJobHandler for TranscodeImport {
         let mut unverified = 0u64;
         let mut failed = 0u64;
         let mut since_checkpoint = 0usize;
+        // Last entry visited, for the tail flush below.
+        let mut last_name: Option<String> = None;
 
         for name in Self::entry_names(&dir).await {
             if let Some(c) = &cursor
@@ -464,11 +466,35 @@ impl RecoverableJobHandler for TranscodeImport {
             }
 
             since_checkpoint += 1;
+            last_name = Some(name.clone());
             if let Some(failure) = checkpoint_if_due(store, &name, &mut since_checkpoint).await {
                 return failure;
             }
         }
 
+        // Flush the tail.
+        //
+        // `checkpoint_if_due` only fires on a full batch, so a run shorter
+        // than BATCH_SIZE never checkpointed at all and reported
+        // `scanned_count: 0` against a known `total_rows` — the admin
+        // progress bar sat at zero through the whole run and finished
+        // there. Longer runs were wrong too, just less visibly: the
+        // remainder after the last full batch was never counted.
+        //
+        // Cursor-wise this is a no-op — the walk is finished, so nothing
+        // will resume from it — but the scanned delta is what the progress
+        // display reads, and it has to include the last partial batch.
+        if since_checkpoint > 0
+            && let Some(name) = last_name
+            && let Err(e) = store
+                .checkpoint(name.into_bytes(), since_checkpoint as u64)
+                .await
+        {
+            return RunOutcome::Failed {
+                message: format!("final checkpoint: {e}"),
+            };
+        }
+
         // Remove the tree once drained. Deletion first, rename only if a
         // non-cache file is in the way — same rule as `.thumbnails/`, and
         // for the same reason: absence is what the read path tests, and a