fix(training): limit CPU threads and epochs to prevent RAM exhaustion

Force CPU-only training (--device cpu), cap OpenMP/BLAS thread pool at 2
(--threads 2), and reduce epochs from 50 to 10 (-N 10). 50 epochs on a
laptop OOM-killed the container. 10 epochs is sufficient for incremental
fine-tuning runs; more data is added over time and training re-run.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ocr-service/main.py

@@ -366,12 +366,13 @@ async def train_model(
             os.makedirs(checkpoint_dir, exist_ok=True)
 
             cmd = [
-                "ketos", "--workers", "0",
+                "ketos", "--workers", "0", "--device", "cpu", "--threads", "2",
                 "train",
                 "-f", "path",
                 "-o", checkpoint_dir,
                 "-q", "fixed",
-                "-N", "50",
+                "-N", "10",
+                "-B", "1",
             ]
             if os.path.exists(KRAKEN_MODEL_PATH):
                 cmd += ["-i", KRAKEN_MODEL_PATH]
@@ -457,11 +458,11 @@ async def segtrain_model(
             os.makedirs(checkpoint_dir, exist_ok=True)
 
             cmd = [
-                "ketos", "--workers", "0",
+                "ketos", "--workers", "0", "--device", "cpu", "--threads", "2",
                 "segtrain",
                 "-o", checkpoint_dir,
                 "-q", "fixed",
-                "-N", "50",
+                "-N", "10",
             ]
             if os.path.exists(blla_model_path):
                 cmd += ["-i", blla_model_path]